Final Thesis 140206

Management of Sweetpotato Whitefly Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) on tomato using

biorational pesticides (Neem, Abamectin and Spinosad) and UV-absorbing nets and films as greenhouse cover in

the humid tropics

Von der Naturwissenschaftlichen Fakultät

der Universität Hannover

zur Erlangung des Grades

Doktor der Gartenbauwissenschaften - Dr. rer. hort. -

genehmigte Dissertation

von

M.Sc. Prabhat Kumar

geboren am 27. December 1970 in Muzaffarpur, India

2005

Referent: Prof. Dr. Hans-Michael Poehling Korreferent: Prof. Dr. Hans-Juergen Tantau Tag der Promotion: 08.02.2006

---- Dedicated to my late grandparents ----

Sri. Ramnandan Mishra ji

&

Smt. Ahilaya Devi

Summary I

Summary

The sweetpotato (Whitefly, WF) Bemisia tabaci Gennadius (Homoptera:

Aleyrodidae) originates from tropical and subtropical regions, now having a

worldwide distribution as a serious pest of open field vegetable production

(Tropics, Sub-tropics and Mediterranean regions) and crops grown under

protected cultivation. The short and multiple life cycles with high reproduction

rates under tropical conditions, fast selection of resistant biotypes to different

classes of insecticides including organophosphates, pyrethroids, cyclodiens and

even first, second generation neurotoxin nicotinoids, and even growth

regulators are major control constraints. In addition, the waxy shelters

protecting the immobile larval and pupal WF stages, high immigration and

generation time, wide range of hosts (over 600 plant species) are

characteristics that make its control extremely difficult.

Subject of the present studies were exploring the potential of the botanical

pesticides, neem using its various application methods and concentrations to

control WF and evaluating its persistency compared to so-called bio-rational

natural pesticides like spinosad and abamectin. In addition, physical control

strategy by using a combination of UV-blocking nets and plastics were explored

to learn their potential to manipulate the immigration behavior (entry) of WF and

other small sucking insect-pest of tomatoes like thrips and aphids taking into

consideration also the thrips related spread of a tospovirus.

In first series of experiments, neem was tested using three different treatment

methods (seed, soil and foliar) and two different commercial neem products

(NeemAzal® T/S 1% Azadirachtin and NeemAzal® U 17% Azadirachtin) against

WF on tomato plants. Studies were conducted in cages in air conditioned

cultivation rooms. All three methods of neem treatments resulted in reduced

colonization and oviposition by WF. Overall oviposition intensity was

significantly reduced by the treatment of tomato seeds (261 eggs in control

compared to 147 eggs at a dose-rate of 3.0g/l of NeemAzal® U) but an even

higher reduction was achieved through soil drenching (345 egg in control

compared to 90 eggs at 3.0g/l of NeemAzal® U) and foliar spraying (286 eggs in

control compared to 53 eggs at 10 ml/l of NeemAzal®) TS. In contrast, in soil

and foliar treatment fecundity per female increased at highest tested

concentrations (from 19 eggs/female in blank treatments to 28 eggs per female

Summary II

at 3.0 g/l NeemAzal® U and from 15 eggs/female to 22 at NeemAzal® TS at 10

ml/l in foliar treatment). Reduced egg hatch could be observed only at high

neem concentrations; 62 and 51% of deposited eggs hatched at highest dose-

rates of NeemAzal®U at 3.0 g/l in case of seed and soil drenching treatments

respectively; whereas only 43% of deposited eggs hatched in case of foliar

treatments at highest dose-rates of 10 ml/l using NeemAzal® T/S. Seed (35%),

foliar (93%) and soil treatments (91%) caused a significantly higher mortality of

immatures and reduced number of hatching adults compared to control plants

treated with a blank formulation or water. The mortality amongst immatures

increased in relation to azadirachtin concentrations. Concerning susceptibility of

different developmental stages, young larvae showed the most sensitive

reaction. The most efficient treatment was foliar treatment, which achieved 100

% mortality for all three larval stages at high concentrations (10.0 ml/l of

NeemAzal® T/S) compared to 78-87% mortality with soil treatment (at 3.0g/l of

NeemAzal® U).

To further explore the possibilities of developing synergy with locally available

parasitoids of WF, persistence of foliar and systemic application of azadirachtin

was tested for 7 days (1,3,5 and 7) in air conditioned rearing rooms and tropical

netted greenhouses using the same two products described for the first

experiments. Foliar application induced under closed room conditions at dose-

rates of 7 and 10 ml NeemAzalTS/l immature mortality of 32 and 44 %

respectively 7-days post application, where as under greenhouse conditions

these rates declined to 5 and 7 % during the same period indicating rapid

dissipation of active ingredient. However, systemic application resulted in more

stable effects under both laboratory and greenhouse conditions. After soil

drenching with solutions of 3.0 g NeemAzalU/l until 7-d, immature mortality

declined from 88% for the first day to almost half (45%) on 7-d. However in case

of laboratory, it was 90% on first day and declined to 64% on 7-d post

application. Similar trends of responses of the B. tabaci were obtained for other

parameters like adult colonization, egg deposition and egg hatch. The loss of

efficiency of the neem products was clearly related to the dose-rate, methods of

application and environment (temperature and UV). Soil application is therefore

a convenient approach to achieve high efficiency and persistence with neem

products under the critical conditions in tropical greenhouse environments.

Summary III

In third experiments, direct and residual toxicity of NeemAzal TS (azadirachtin),

spinosad (Spinosyne) and abamectin (Avamectin) were tested against different

life stages of WF under laboratory conditions and in a tropical net greenhouse.

NeemAzal TS and abamectin deterred the settling of adults on the plant and

consequently reduced egg deposition. No such effect was detected for

spinosad. All three pesticides influenced egg hatch. Effects of NeemAzal TS

were significantly altered if applied to different aged eggs (1, 3, and 5-d old). In

contrast, abamectin treated eggs failed to hatch at any given age-class.

Moreover, spinosad and NeemAzal TS influenced egg hatch in a concentration

dependent manner. All three products caused heavy mortality of all three larval

stages of B. tabaci, where the first instar larvae was found to be most

susceptible compared to other two larval stages. Larval mortalities of 100%

were achieved with NeemAzal TS at twice the recommend dose-rate (10ml/l)

and at all tested concentrations of abamectin and spinosad. The daily mortality

rates were highest for abamectin, all treated larvae at every larval stage died

within 24 h post application. In contrast, 100% larval mortality in case of

NeemAzalTS and spinosad was reached 6-9 days post application. The daily

mortality rates were clearly concentration dependent. Abamectin caused 100%

immature mortality at all residue ages (1, 5, 10 and 15-d) in the laboratory and

greenhouse as well. Persistence of spinosad was comparable high in the

laboratory but in the greenhouse a faster decline of activity was evident by

increased egg deposition, egg hatch and reduced rates of immature mortality.

Toxicity of NeemAzalTS however strongly declined under greenhouse

conditions with time (5-d) post application.

The last series of experiments explored the possibility of integrating UV-

blocking nets and plastics to develop appropriate physical control strategies for

WF. The studies were conducted to investigate the effect of ultraviolet blocked

greenhouses made from combination of net and plastics on the immigration of

three important pest of tomatoes; WF (Bemisia tabaci), thrips (Ceratothripoides

claratris), and aphid (Aphis gossypii) and occurrences of viruses e.g. tospovirus.

Fewer WF, aphids and thrips immigrated and consequently were trapped either,

when gates kept open whole day (complete ventilation) or partially open from

6.00 � 10.00 (partial ventilation) in greenhouses made from the combination of

UV-blocking nets and plastics compared to non UV-blocking nets and plastic

Summary IV

greenhouse. Similarly, significantly less number of alate aphids and adult B.

tabaci/leaf were counted within greenhouses with low intensity of the UV over

those with more UV light intensity. Thrips were the most occurring pests, that

too were recorded significantly less under GH with lower UV-intensity and

consequently significantly lower levels of leaf damage were recorded under

these greenhouses. During, open gates experiments (complete ventilation), a

96-100% virus infestation was recorded under non UV-blocking greenhouses

compared to 6-10% under UV-blocking greenhouses, having majority of the

plants tested positive for the tospovirus, CaCV (isolate AIT). The virus spreads

were remarkably delayed for several days under greenhouses with lower UV

light. These results suggests that greenhouses made from the combination of

the UV-blocking nets and plastics have a significant influence on the both the

immigration and virus spread vectored by some of these insects. The results

are discussed in context of improved management of sucking insect-pests of

tomatoes in the humid tropics under protected cultivation.

Keywords: Bemisia tabaci, Biorationals, UV-blocked greenhosues

Zusammenfassung V

Zusammenfassung Die Weiße Fliege (WF) Bemisia tabaci Gennadius (Homoptera: Aleyrodidae)

ursprünglich aus den Tropen und Subtropen stammend ist heute weltweit

verbreitet und ein bedeutender Schädling im Feldgemüsebau wärmerer

Klimaregionen aber auch vieler Gewächshauskulturen der gemäßigten Zonen.

In den Tropen führen der kurzen Entwicklungszyklus mit multiplen

Generationen im Jahr zusammen mit hohen Reproduktionsraten zu schnellen

und dauerhaften Massenvermehrungen. Die intensive Anwendung von

Insektiziden führt unter diesen Bedingungen zu einer schnellen Selektion

insektizidresistenter Biotypen. Resistenz ist heute gegenüber verschiedenen

Wirkstoffgruppen belegt, so organischen Phosphorsäureestern, Pyrethroiden,

Cyclodienen und jüngst sogar den erst seit wenigen Jahren eingesetzten

Nicotinoiden und Wachstumsregulatoren. Zudem werden die immobilen

Larvenstadien und das Entwicklungsstadium im Puparium durch

Wachsüberzüge vor Kontaminierung mit Kontaktinsektiziden geschützt.

Aufgrund der großen Polyphagie (bis zu 600 Pflanzenarten sind als

Wirtspflanzen bekannt) besteht in der Regel ein hoher Immigrationsdruck in neu

etablierte Kulturen. Diese Faktoren insgesamt machen eine effektive Kontrolle

allein mit herkömmlichen Insektiziden außerordentlich schwierig, zudem sind

dabei aufgrund der Toxizität und Persistenz vieler Wirkstoffe erhebliche Risiken

für Farmer und Konsumenten gegeben.

Ziel der hier vorgestellten Studien ist die Analyse des Potentials des

botanischen Insektizids Neem unter Berücksichtigung verschiedener

Applikationstechniken und Aufwandmengen zur Kontrolle von B. tabaci und

eine Bewertung der Persistenz im Vergleich zu den sogenannten

�Biopestiziden� Spinosad und Abamectin, die Produkte natürlicher

Bodenorganismen sind. Zusätzlich sollten Möglichkeiten der Manipulation des

Einwanderungsverhaltens von WF mittels UV-sorbierender Netze und Folien

untersucht werden, wobei auch andere mobile saugende Schädlinge der

Tomate wie Thripse und Blattläuse einbezogen wurden und der Übertragung

von Tospoviren durch Thripse ein besonderes Augenwerk geschenkt wurde.

In einer ersten Serie von Experimenten wurde die Wirkung von zwei

kommerziellen Neem-Präparaten (NeemAzal® T/S (1% azadirachtin) and

NeemAzal U® (17% azadirachtin)) auf B. tabaci bei verschiedenen

Zusammenfassung VI

Applikationsmethoden (Saatgutbehandlung, Boden- und Blattapplikation)

untersucht. Die Untersuchungen erfolgten in Käfigen in klimatisierten

Zuchträumen. Alle drei Anwendungsverfahren führten zu einer verringerten

Besiedlung der Tomatenpflanzen und zu reduzierter Eiablage. Insgesamt war

die Intensität der Eiablage durch die Behandlung der Samen signifikant

vermindert (261 Eier in der Kontrolle im Vergleich zu 147 Eier bei einer

Aufwandmenge von 3,0g/l of NeemAzal® U). Eine intensivere Reduktion wurde

durch die Bodenbehandlung (345 Eier in der Kontrolle im Vergleich zu 90 Eiern

bei 3,0g/l of NeemAzal® U) und durch eine Sprühbehandlung der Blätter (286

Eier in der Kontrolle verglichen mit 53 Eiern bei 10 ml/l of NeemAzal TS®))

erreicht. Im Gegensatz dazu wurde bei Boden- und Blattbehandlungen eine

höhere Fekundität pro Weibchen bei den höchsten geprüften Konzentrationen

beobachtet (von 19 Eiern/Weibchen in Kontrollen bis zu 28 Eiern pro Weibchen

bei 3,0 g/l NeemAzal U® und von 15 Eiern/Weibchen bis zu 22 mit NeemAzal

TS® bei einer Aufwandmenge von 10 ml/l).

Ein reduzierter Schlupf der Eilarven konnte nach Anwendung hoher Neem

Konzentrationen beobachtet werden; 62% und 51% der abgelegten Eier

schlüpften bei der höchsten Dosierung von NeemAzal® U (3,0 g/l) bei Samen-

und Bodenbehandlungen während nur 43% der Eier im Fall von

Blattapplikationen mit hohen Aufwandmengen von 10 ml/l NeemAzal® T/S

schlüpften. Samen- (35%), Blatt- (93%) und Bodenbehandlungen (91%) führten

zu signifikant höheren Mortalitätsraten der Larvenstadien und verringerten die

Anzahl schlüpfender Adulter verglichen mit Kontrollbehandlungen. Dabei nahm

die Mortalität mit zunehmender Konzentration an azadirachtin zu. Die höchste

Empfindlichkeit zeigten junge Entwicklungsstadien. Die effizienteste

Applikationsform stellte die Blattbehandlung dar, mit der eine 100 %ige

Mortalität aller drei Larvenstadien bei hohen Dosierungen (10,0 ml/l

NeemAzal® T/S) erreicht werden konnten, verglichen mit 78-87% Mortalität bei

Bodenbehandlungen (3,0g/l NeemAzal®U).

Weiterhin wurde die Persistenz der Wirkung von Blatt- und Bodenapplikation

von Azadirachtin überprüft, indem die Behandlungen in einem maximalen

Zeitraum von 7 Tagen (1, 3, 5 und 7 Tage) vor der Besiedlung durch B. tabaci

durchgeführt wurden. Die Behandlungen wurden vergleichend in klimatisierten

und vor UV-Licht geschützten Räumen sowie in Netzhäusern mit freier

Zusammenfassung VII

Sonneneinstrahlung angelegt. Blattbehandlungen induzierten unter den

Bedingungen der klimatisierten Zuchträume bei Dosierungen von 7 and 10 ml

NeemAzalTS/l eine Larvalmortalität von 32% und 44 % auf sieben Tage vor

Besiedlung behandelten Pflanzen wohingegen unter

Gewächshausbedingungen diese Raten auf 5% und 7 % abnahmen und damit

den schnelleren Abbau der aktiven Substanzen im Gewächshaus

dokumentierten. Die systemischen Behandlungen resultierten in stabileren

Effekten unter beiden äußeren Bedingungen. Nach Bodenbehandlung mit 3,0 g

NeemAzalU/l nahm die Larvenmortalität von 88% auf 45% innerhalb von Tag

eins bis sieben im Gewächshaus, im Labor nur von 90% auf 64% ab. Ähnliche

Trends in der Reaktion von B. tabaci wurden auch bei anderen Parametern

beobachtet wie dem Schlupf von Adulten, der Eiablage und dem Eischlupf.

Abnehmende Effizienz war jeweils verknüpft mit abnehmender Dosierungsrate,

der Behandlungsmethode und den Umweltfaktoren (Temperatur, UV).

Bodenbehandlungen mit Neem bieten somit einen geeigneten Ansatz eine hohe

Effizienz zusammen mit einer hohen Persistenz zu erreichen selbst unter den

kritischen Bedingungen tropischer Gewächshäuser.

In einem dritten Experiment wurden direkte und residuale Effekte von

NeemAzal TS (azadirachtin), Spinosad (Spinosyne) and Abamectin (Avamectin)

auf verschiedene Entwicklungsstadien der Weißen Fliege unter

Laborbedingungen und in tropischen Gewächshäusern vergleichend

untersucht. NeemAzal TS and Abamectin übten einen Deterrent-Effekt auf die

Ansiedlung der Adulten auf den Pflanzen aus mit der Konsequenz einer

Reduktion der Eiablage. Entsprechendes konnte für Spinosad nicht beobachtet

werden. Alle drei Insektizide beeinflussten zudem den Eischlupf. Die Effekte

von NeemAzal TS prägten sich significant unterschiedlich aus, wenn

unterschiedlich alte Eistadien (1, 3, und 5 Tage alt) behandelt wurden. Im

Gegensatz dazu wurde der Eischlupf durch Abamectin vollständig bei allen

Alterklassen der Eier unterbunden. Zudem beeinflussten Spinosad und

NeemAzal TS den Eischlupf konzentrationsabhängig. Alle drei Produkte führten

zu hoher Mortalität der Larvenstadien von B. tabaci. Das erste Stadium erwies

sich als besonders empfindlich. Larvalmortalitäten von 100% wurden mit

NeemAzal TS bei einer Aufwandmenge von 10ml/l und allen Dosierungen von

Abamectin und Spinosad erreicht. Die täglichen Mortalitätsraten waren am

Zusammenfassung VIII

höchsten für Abamectin, alle behandelten Larven und alle Larvalstadien starben

innerhalb von 24 Stunden nach Behandlung. Im Gegensatz dazu wurde eine

100% Larvalmortalität im Fall von NeemAzalTS und Spinosad 6-9 Tagen nach

Behandlung errreicht. Die täglichen Mortalitätsraten waren klar

konzentrationsabhängig. Abamectin führte zu einer 100% igen Abtötung der

Larven bei allen Altersgruppen der Spritzbeläge (1, 5, 10 und 15 Tage) im

Labor wie auch im Gewächshaus. Die Persistenz von Spinosad war im Labor

vergleichbar hoch, nahm jedoch im Gewächshaus schneller ab, erkennbar an

zunehmender Eiablage, erhöhtem Eischlupf und einer reduzierten

Larvalmortalität. Die Wirkung von NeemAzal TS hingegen nahm unter

Gewächshausbedingungen mit der Zeit besonders stark ab.

Die letzte Serie von Experimenten analysierte die Möglichkeit UV-sorbierende

Netze und Folien als physikalische Kontrolle von WF zu nutzen. Die

Untersuchungen wurden durchgeführt, um den Einfluß UV blockierender

Gewächhausmaterialien als Kombination von Netzen und Folien auf die

Einwanderung von drei bedeutenden Schädlingen der Tomate, der Weißen

Fliege Bemisia tabaci, dem Thrips Ceratothripoides claratris, und der Aphide

Aphis gossypii einschließlich des Auftretens von Virosen (Tospoviren) zu

erfassen. Weniger Weiße Fliegen, Aphiden und Thripse immigrierten in die

Gewächshäuser, die mit einer Kombination UV sorbierender Netze und Folien

bespannt waren, obwohl die Tore ganztägig oder teilsweise (6.00 � 10.00) zur

Ventilation offen gehalten wurden. Gleichermassen wurden weniger geflügelte

Aphiden und Adulte B. tabaci pro Blatt in Gewächshäusern mit einer geringen

Intensität an UV verglichen mit Häusern, die höhere UV Intensität innen

aufwiesen, gezählt. Thripse waren besonders abundant und wurden ebenfalls

signifikant weniger in GH´s mit niedriger UV Intensität gefangen.

Konsequenterweise ergaben sich signifikant geringere Schadsymptome an den

Blättern. Mit offen Türen und normalen nicht UV blockierenden

Gewächhausmaterialien wurden Virussymptome an 96 bis 100% der Pflanzen

festgestellt, während nur 6 bis 10% der Pflanzen in UV sorbierenden Häusern

infiziert wurden. Die Mehrzahl der Pflanzen mit visuelle erkennbaren

Symptomen wurde positiv auf das Tospovirus CaCV (Isolat AIT) getestet. Die

Virusausbreitung war deutlich verzögert unter geringen UV Intensitäten. Diese

Ergebnisse deuten an, daß Gewächshäuser aus den erwähnten Materialien

Zusammenfassung IX

signifikant zur Reduzierung der Immigration saugender Schädlinge und

Virusausbreitung beitragen können. Die Ergebnisse werden im Hinblick auf ein

verbessertes integriertes Management saugender Insekten an Tomaten in den

humiden Tropen unter Bedingungen des geschützten Anbaus diskutiert.

Stichworte: Bemisia tabaci, Biopestiziden, UV-sorbierende Netze und Folien

Contents X

Contents

1. General Introduction 1 2. Use of seed, soil and foliar treatments of azadirachtin to

control Sweetpotato Whitefly Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) on tomato plants1

2.1 Introduction 13

2.2 Materials and Methods 15

2.3 Results 18

2.4 Discussion 24

3. Persistence of soil and foliar azadirachtin treatments to control Sweetpotato Whitefly Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) on tomatoes under controlled (laboratory) and field (netted greenhouse) conditions in the humid tropics2

3.1 Introduction 28


3.3 Results 33

3.4 Discussion 45

4. Effects of Azadirachtin, Abamectin and Spinosad on Sweetpotato Whitefly Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) on tomato plants under laboratory and greenhouse conditions in the humid tropics 3

4.1 Introduction 50


4.3 Results 56

4.4. Discussion 67

Contents XI

5. Impact of UV-blocking plastic covers and netting on the pest status of Bemisia tabaci Gennadius (Homoptera: Aleyrodidae), Ceratothripoides claratris Shumsher (Thysanoptera: Thripidae) and Aphis gossypii Glover (Homoptera: Aphididae) on tomatoes in the humid tropics4

5.1 Introduction 72


5.3 Results 79

5.4. Discussion 94

6. Final Discussion 99 7. References cited 104

Acknowledgements 133

Contents XII

1 Part of this chapter was published as: Kumar, P., H.-M. Poehling and C.

Borgemeister. 2005. Effects of different application methods of azadirachtin

against sweetpotato whitefly Bemisia tabaci Gennadius (Hom., Aleyrodidae) on

tomato plants. J. Appl. Entomol. 129 (9/10), 489�497.

2 Kumar, P., and H-M. Poehling. Persistence of soil and foliar azadirachtin

treatments to control Sweetpotato Whitefly Bemisia tabaci Gennadius

(Homoptera: Aleyrodidae) on tomatoes under controlled (laboratory) and field

(netted greenhouse) conditions in the humid tropics. Submitted to Journal of

Pest Sciences.

3 Kumar, P., and H-M. Poehling. Effects of Azadirachtin, Avamectin and

Spinosad on Sweetpotato Whitefly Bemisia tabaci Gennadius (Homoptera:

Aleyrodidae) on tomato plants under laboratory and greenhouse conditions in

the humid tropics. Submitted to Journal of Economic Entomology.

4 Kumar, P., and H-M. Poehling. Impact of UV-blocking plastic covers and

netting on the pest status of Bemisia tabaci Gennadius (Homoptera:

Aleyrodidae), Ceratothripoides claratris Shumsher (Thysanoptera: Thripidae)

and Aphis gossypii Glover (Homoptera: Aphididae) on tomatoes in the humid

tropics. Submitted to Environmental Entomology.

Abbreviations XIII

Abbreviations

AIT Asian Institute of Technology

ANOVA Analysis of variance

arcsin√ Arcsine�square-root

Ca Calcium

CaCV Capsicum chlorosis virus

d day

d.f. Degree of freedom

DAS-ELISA Double antibody sandwich enzyme-linked immunosorbent

assay

DoA Department of Agriculture, Royal Govt. of Thailand

F Statistical F-value

g/l Grams per liter

GBNV Groundnut bud necrosis virus

GH Greenhouse

GHs Greenhouses

GHWF Greenhouse whitefly (Trialeurodes vaporaiorum)

h Hours

ha Hectare

IPM Integrated pest management

K Potassium

L : D Relation of light to darkness

Lab Laboratory

L1 First instar larva

L2 Second instar larva

L3 Third Instar lava

LSD Least significant difference

Abbreviations XIV

ml/l Milliliters per liter

Mt Million tons

N Nitrogen

P Statistical probability value

P Potassium

rH Relative humidity

SAS Statistical analysis system

SE Standard error

t Statistical t-value

UV-B Ultraviolet blocking

UV-NB Ultraviolet Non-blocking

WF Whitefly (Bemisia tabaci)

General Introdcution 1

General Introduction

Tomato, Lycopersicon esculentum (Mill) (Solanaceae) originated from the South

America in the Peru and Ecuador region, is now widely cultivated throughout

the world in tropical, sub-tropical and temperate climatic zones (Tindall 1983,

Taylor 1986). Tomato was brought to the Asian continent by the Spanish

colonists, first to the Philippines, from where, it moved to Southeast Asia and

then to the entire Asian continent (Anonymous 2005a, see fig. 1.1).

Tomato is very good source of Vitamin A, B and excellent source of Vitamin C

(Madhavi and Salunkhe 1998). The area under tomato production in Asia has

doubled in last decade from 1,440,744 to 2,585,292 ha and production

increased from 33,232,543 to 59,662,771 Mt in 2004 (FAOSTAT 2005). In

Thailand, the tomato area increased from 9,760 ha in 1994 to 10,200 ha in 2005

with a total production of 248,000 Mt (FAOSTAT 2005) and it is widely grown in

all regions but concentrated in the central and north-eastern part of Thailand

(Anonymous 2005b).

The realization of optimal yields of vegetable crops including cultivated

tomatoes, particularly in the warm humid lowlands of the tropics, is often

constrained by a number of serious arthropod pests and viral diseases vectored

by them (Deang 1969, Gomaa et al. 1978, Lange and Bronson 1981, Berlinger

et al. 1988, Kakar et al. 1990, Berlinger 1992, Jinping 1994, Ketelaar and

Kumar 2002). Tomato production in Thailand is constrained by WF (Bemisia

tabaci), Thrips, Leafminers, Fruit worm (Helicoverpa sp.), etc. and among them

Bemisia vectored TYLCV is major production constraints (Attathom et al. 1990,

Sawangjit et al. 2005). About 1300 whitefly species in over 120 genera have

been described (Anonymous 2001, Mound and Halsey 1978) and the genus

Bemisia contains at least 37 species (Mound and Halsey 1978). The genus is

thought to have originated in Asia with Bemisia tabaci being of possible Indian

origin (Fishpool and Burban 1994). The first B. tabaci in the New World were

collected in 1897 in the United States on sweetpotato. It was originally

described as Aleyrodes inconspicua Quaintance and given the common name

of sweetpotato whitefly (Quaintance, 1900).

1


Fig. 1.1. Distribution of tomato cultivation area and B. tabaci presence in Asia1

In 1928, it was found in Brazil described as B. costalimai Bondar (Mound and

Halsey 1978) and in 1933, in Taiwan and described as B. hibisci (Mound and

Halsey 1978). Further, B. tabaci spread to other geographical range from

subtropical and tropical agriculture systems has occurred to include temperate

climate areas; the species is now globally distributed and found on all

continents except Antarctica (Martin 1999, Martin et al. 2000). It is widely

present in most of the countries in Asia (see figure 1.1). B. tabaci was first

described as a pest of tobacco in Greece in 1899 (Cock 1986). In warmer

regions (Tropics, Mediterranean), it is a serious pest in open field vegetable

production but crops grown under protected cultivation (film tunnels, net

houses) are equally suffering from heavy infestation with WF and severe

damage is frequently reported. In addition, it has recently become a significant

pest of protected horticulture in temperate regions (Butler and Heneberry 1986,

Denholm et al. 1996). WF has been recorded in over 600 different plant species

(Mound & Halsey 1978, Greathead 1986, Cock 1986, Secker et al. 1998) and

can easily adapt to a new environment. It feeds on a wide variety of

dicotyledonous horticultural crops such as tomato, pepper, beans, eggplant and

cucumber. 1 Source: Crop Protection Compendium, CAB International 2002 ed.

Bemisia tabaci

Tomato


The polyphagous nature of Bemisia tabaci has been documented worldwide

(Bird 1957, Costa and Russell 1975, Bird and Marmorosch 1978, Butler et al.

1986, Costa and Brown 1990 & 1991, Costa et al. 1991, Burban et al. 1992).

Large numbers of cultivated crops, weeds, non-cultivated annual and perennial

plant species are reported in several studies as acceptable feeding and/or

reproductive hosts (Butler and Henneberry 1986, Bedford et al. 1992, 1994,

Brown et al. 1992 &1995). Of the total host-plant species listed by Mound and

Halsey (1978), almost half belong to five families: Fabaceae, Asteraceae,

Malvaceae, Solanaceae and Euphorbiaceae. Tomato is one of the major

vegetable hosts of the Bemisia in Thailand beside a root /starch crop Cassava.

B. tabaci adult and nymphs damages the tomato crops directly through sap

feeding, produces massive quantities of honeydew that encourages the growth

of sooty mould on leaves inhibiting photosynthesis and causing cosmetic

damage (De Barro 1995). It causes uneven ripening of tomato (see fig. 1.2 (B);

Maynard and Cantliffe 1989, Bharathan et al. 1990, Yokomi et al. 1990,

Schuster et al. 1990, Matsui 1992), and on vegetables, melons, and

ornamentals, honeydew and sooty mould reduce quality and marketability (Riley

and Palumbo 1995).

An indirect effect of feeding by some whiteflies is the transmission of plant

viruses, many of which are of economic importance. Whitefly instar nymphs and

adults feed by inserting their proboscises into the leaf, penetrating the phloem

and withdrawing sap. It is during this feeding process that plant viruses are

acquired. Adult whiteflies may disperse and transmit the virus to new plants

while feeding (Jones 2003). B. tabaci has been of increasing importance as a

pest and vector of virus diseases of food, fiber and ornamental plants since the

early 1980s. This has been due to the emergence of the B biotype and its rapid

expansion in geographic distribution and host range. The whiteflies, and the

viruses it transmits, are now responsible for significant crop losses in many

regions with tropical, subtropical, arid and Mediterranean climates. Cassava,

cotton, cowpea, cucurbits, crucifers, tobacco, tomato, potato, soybean, sweet

potato, okra, lettuce, pea, bean, pepper, poinsettia and chrysanthemum are

some of those crops that are vulnerable (De Barro 1995).


Fig. 1.2. Sooty mould growth on tomato (A)2; uneven ripening in tomato (B)3;

Tomato Yellow Leaf Curl Virus infected tomato plant (C).

B. tabaci is a vector of 111 plant viruses recognized as species in the genera

Begomovirus (Geminiviridae), Crinivirus (Closteroviridae), Carlavirus or

Ipomovirus (Potyviridae) (Jones 2003). Begomoviruses are the most numerous

of the B. tabaci-transmitted viruses and cause crop yield losses of between 20%

and 100% (Brown and Bird 1992, Rapisarda and Garzia 2002) and its

symptoms includes yellow mosaics, yellow veining, leaf curling, stunting and

vein thickening (Anonymous 2001). 2 http://www.crop.cri.nz/home/products-services/publications/broadsheets/91.pdf. (Assessed on 16.09.2005) 3 http://whiteflies.ifas.ufl.edu/wfly0013.htm. (Assessed on 15.09.2005)

C

BA


In conclusion, the high degree of polyphagy, ingestion of large amounts of

phloem sap by feeding and transmission of plant viruses between hosts all

contributes to the pest status of this species (Duffus 1987, Byrne et al. 1990).

The Bemisia life cycle consists of egg, 3 nymphal (larval) instars, pupal and

adult stage. The eggs are about 0.2 mm long and pear shaped. They are laid on

the under surface of young leaves. After hatching, individuals during their

immature stages also stay on the under surface of leaves. The first instar

nymphs (crawlers) move a very short distance after hatching over the leaf

surface until they find a suitable site for feeding. Once settled, they remain

sessile until they reach the adult stage, except for brief periods during moults.

The fourth instar (the so called �pupa�) is about 0.7 mm long. Its red eye spots,

which become eyes at the adult stage, are characteristic of this instar (Hill and

Walker 1991, Kumar P. 2005 unpublished data). In a study on life cycle of B.

tabaci from Thailand, Charungphan (2002) reported that pre-oviposition period

of female WF was 1.38±0.49 days (1-2 day) and the oviposition period was

5.03±1.17-d. The number of eggs/female averaged 73.97±14.01 and incubation

period was 6.60±0.84 �d. The nymphs underwent three instars of development

and duration of each successive three instars was 2.84±0.75 days; 3.34-d;

2.59±0.61-d. respectively. The total nymphal period was 8-10 days; pupal

duration was 5-7 days (see fig. 1.3 A-E; Charungphan 2002, Kumar P. 2005

unpublished data).

The direct damage of B. tabaci adult and nymphs along with its virus

transmission abilities lead to high losses in tomato production in Thailand.

Therefore, suitable management strategies against B. tabaci are urgently

needed to reduce the overall loss of yield and quality of tomato production.

Chemical based pest management strategies are common feature of Asian

vegetable production and tomato production in Thailand is not an exception in

this regard. Thailand is a major market for pesticides with an annual growth rate

since1982-92 of 8.8%, with some slowing down since then.


Fig.1 3. (A-E). Some important development stages of the of Bemisia tabaci4

4 1.3 (B) Source: http://www.entocare.nl/nl/foto's/images/Bemisia_tabaci_larve.jpg). Accessed on 15.09.2005

1.3 (F) Source: http://www.whitefly.org/UnderConst.asp). Assessed on 15.09.2005

E: Freshly emerged adult

C: empty pupal case D: A pupa

A: Eggs B: Immatures of B. tabaci

F: An emerging adult from puparia


Thailand is one of the biggest users of pesticides in the Southeast Asian region

with an annual sales amounted in 1994 was US$247 million. Lot of pesticides

are imported and, of imported pesticides, 73% fall into the WHO hazard

categories Ia, extremely hazardous, and Ib, highly hazardous, and a further

33% are category II, moderately hazardous category (Jungbluth 1996).

Between 1980 and 1999 the quantity of pesticides imported to Thailand has

increased from 9,855 to 33,969 tons, at an annual growth rate of 6.7%

(Anonymous, 2002). In Thailand, misuse and over-use of pesticides results into

39,600 pesticide poisoning cases a year, with total annual health costs of about

13 million Baht5 (Jungbluth 1996). Unlike some other SE Asian counties like

Indonesia, the overall pesticide market in Thailand still remain largely

unaffected by national and international IPM efforts (Oudejans 1999).

Several work have been reported so far against insecticidal management of the

Bemisia tabaci in tomato crop e.g. pyrethroids or combination of conventional

pesticides (Schuster 1994 &1995a, b, Stansly and Cawley 1994a, Stansly and

Conner 1995). Despite the fact that the larval stages of the WF are susceptible

to these active ingredients (Prabhaker et al. 1989), control of immature

populations on plants with conventional treatments is inherently difficult to

achieve, because the sessile nymphs reside on the abaxial surface of leaves

and are difficult to contact with sprays (Palumbo and Coates 1996). Similarly, lot

of work were reported against B. tabaci on tomato using novel first generation

neurotoxic nicotinoids like imidacloprid either as foliar spray or pre or post

planting drench with some but variable success for B. tabaci management in

tomato (Schuster (1993a, 1993b, 1995, 1996, 1997a&b, 1998, 2000a and

2000b); Schuster and Polston, (1997a & b, 1998). Moreover, imidacloprid failed

to prevent the transmission of the TYLCV in a recently reported study

(Rubinstein et al. 1999). A more successful use is reported for the second

generation nicotinoids like Thiamethoxam, Acetamiprid, Thiamethoxam either

as foliar sprays or drench (Schuster and Polston 1998, Stansly and Conner

1998, Stansly et al. 1999, Schuster 2000 a & b, Stansly and Conner 2000).

5 1 US $ = 41 Thai Baht (approximately) as of Nov. 2005


However this compound also failed to provide an effective and reliable

management of the TYLCV spread and gave so far only inconsistent results

(Schuster 2000a, Stansly and Conner 2000).

Insect growth regulators are yet another group of novel chemistry, a being

successfully integrated for management of B. tabaci in vegetable cropping

ecosystem with good success (Palumbo et al. 2001). The major limitations in

using these very effective growth regulators are their restrictive effects on only

certain life stages of B. tabaci and rapid development of resistance (Horowitz et

al. 1999a & b, Denholm et al. 1998, Ellsworth et al. 1996, Dennehy et al. 1996).

Rapid development of resistance against insecticides has been well document

in B. tabaci for several conventional insecticides, alone or in combination,

(Dittrich et al. 1990a, Cahill et al. 1995, Horowitz and Ishaaya 1996, Denholm et

al. 1996). The high potential of B. tabaci to develop resistance is documented

by the recent development against the chloronictinyls as well. Resistance of B.

tabaci against Imidacloprid as first leading compound of this group is more and

more often reported (Prabhaker et al. 1997, Denholm et al. 1998, Cahill and

Denholm 1999, Elbert and Nauen 2000) and even the repeated application of

second generation nicotinoids like acetamiprid resulted in 5-10 fold decrease in

susceptibility of B. tabaci to the compound (Horowitz et al. 1999a). Furthermore

IGR`s with a unique mode of action have proven select resistant populations of

B. tabaci (Horowitz and Ishaaya 1994, Cahill et al. 1996, Elbert and Nauen

2000).

To avoid selection of resistant biotypes (Talekar and Shelton 1993, Williams

and Dennehy 1996), a careful management with frequent changes of active

ingredients (change of targets) is necessary. Control with insecticides is not

only difficult because of resistance but also to its deleterious effect on natural

enemies, contamination of water sources, and direct health hazards to both

farmers and consumers (Saha 1993). Pronounced systemic properties of the

pesticides are needed because WF feeding sites are on the abaxial surface of

leaves and by production of their wax shelters they are difficult to target by

contact poisons (James 2003). Short time after immigration, typically all

developmental stages of WF are continuously present on the plants (Prabhaker

et al. 1989); any control strategies not targeting all development stages of the


WF would be insufficient. This is particular important for the partly feeding pupal

stages. Furthermore, according to the philosophy of Integrated Pest

Management (IPM) effective pesticides but with low mammalian toxicity, low

persistence in the environment and high degree of selectivity are desired. Along

with so called �bio-pesticides� several others environmentally sound

management techniques are recommended like use of resistant varieties (de

Jager and Butot 1993, Shelton et al. 1998) and/or habitat management (Suzuki

and Miyara 1984, Riddell-Swan 1988). Biological control using aphelinid

parasitoids like Encarisa sp. and Eretmocerus sp. has played an important role

in the control of the whitefly in greenhouses and in field world wide (van

Lenteren et al. 1980, van Lenteren 1983, Hoddle et al. 1998) but till date no

candidate has been widely used and adopted in the humid tropics.

To overcome most of the mentioned problems related to chemical pesticides so

called biopesticides like neem and two recent novel pesticides of microbial

origin spinosad and abamectin along with physical control options like Ultra-

violet blocking plastics and nets are discussed as promising candidates but

have to be critically tested under the dynamic and extreme conditions of the

humid tropics before they could become a good and accepted option for both

protected crops as well as field crops.

Azadirachtin (neem), a steroid-like tetranortriterpenoid derived from neem trees

(Azadirachta indica Juss.), is a strong anti-feedent, repellent and growth

regulating compound for a wide variety of phytophagous insects, including WF.

It delays and prevents moulting, reduces growth, development and oviposition;

and can cause significant mortality particularly in immatures (Coudriet et al.

1985, Flint and Sparks 1989, Prabhaker et al. 1989, Schmutterer 1990, Liu and

Stansly 1995, Mitchell et al. 2004). Neem preparations are commercially

available in most countries in the humid tropics for control of plant sucking

insects including WF; however the efficacy seems to be highly variable

particularly under field conditions (Puri et al. 1994, Leskovar and Boales 1996,

Akey and Henneberry 1999). The major drawback of neem and neem based

triterpenoids is their rapid dissipation and degradation in presence of light,

which can reduce its bio-efficacy considerably (Stokes and Redfern 1982,

Barnaby et al. 1989, Johnson et al. 2003, Barrek et al. 2004).


Spinosad (Spinosyn A, 85%: Spinosyn D, 15%) is a bio-rational pesticide

derived from aerobic fermentation of the actinomycete soil bacterium

Saccharopolyspora spinosa with a world wide use on over 200 crops against

insect-pests of several orders like Lepidoptera, Diptera, Thysanoptera,

Siphonaptera, Coleoptera and Hymenoptera etc. and with high selectivity

concerning mammals or wildlife. It is classified as a reduced-risk pesticide by

the US Environment Protection Agency (Cleveland et al. 2001). However, it is

relatively less active against mites and sucking insect-pests (Boek et al. 1994,

Dow 1997, Bret et al. 1997, Thompson et al. 2000). Spinosad acts through

ingestion and contact and kills the insects through action on their nervous

system (Salgado 1997 and 1998, Thompson et al. 2000, Cowles et al. 2000,

Tjosvold and Chaney 2001). For non-target insects and beneficial its toxicity is

quite specific. Whereas, selectivity is described for mammals or wildlife fresh

residues are described to affect pollinators like Honey Bees or Bumble Bees

(Miles et al. 2002, Mayes et al. 2003, Morandin et al. 2005). It is moderately

toxic to commonly used biological control agents like Amblyseius cucumeris

Oudeman (Acarina; Phytoseiidae) and Orius indidiosus Say

(Hemiptera:Anthocoridae) (Pietrantonio and Benedict 1999, Ludwig and Oetting

2001). However, it was found highly toxic to the commonly used whitefly

parasiotid, Encarsia formosa (Hym: Aphelinidae) even after 28-day post

application (Jones et al. 2005) or the egg parasiotid Anaphes iole

(Hymenoptera: Mymaridae) (Williams III et al. 2003) to give only two striking

examples. The persistency of spinosad is limited to few days in presence of

sunlight (Saunders and Brett 1997), thus devoid of any long term persistent

effects to the natural enemies.

Abamectin is also derived from a soil bacterium Streptomyces avermitilis

(avermectins: 80% avermectin B1a and 20% avermectin B1b) and it acts by

affecting the nervous system of insects. It is highly toxic to a broad spectrum of

insects if they are contaminated by fresh spraying solutions or residues and

mammals can be affected if ingesting too high dosages since the LD 50 value is

in the toxic range (Ray 1991). Similar to spinosad, it is highly toxic to the honey

bees and other pollinators and to water organism but it is subject to rapid

degradation when present as a thin film, as on treated leaf surfaces. Under


laboratory conditions and in the presence of light, its half-life is short, regardless

of surface or foliage type (Wislocki et al. 1989).

Abamectin does not persist or accumulate in the environment. Its instability as

well as its low water solubility and tight binding to soil, limit abamectin's

bioavailability for non-target organisms and, furthermore, prevent it from

leaching into groundwater or entering the aquatic environment (Lasota & Dybas

1990).

Some species of insects like whitefly, thrips and aphids have been shown to be

dependent on UV light to orient themselves during flight and may use UV-light

reflectance patterns as cues in recognizing host plants and flower species

(Kring 1972, Rossel and Wehner 1984, Scherer and Kolb, 1987, Greenhough et

al. 1990, Kring and Schuster 1992, Gold Smith 1993, Costa and Robb 1999).

Furthermore this idea was supported by previous findings that Bemisia

argentifolii and Frankliniella occidentalis are attracted to the UV light (Mound

1962, Matteson and Terry 1992, Antignus et al. 1996, Antignus 2000) and

incidence of aphids and aphid-borne virus diseases were delayed and reduced

by use of UV-blocking plastic mulches in squash and other crops (Brown et al.

1993, Summers and Stapleton 1998, Stapleton and Summers 2002). Field

studies from Israel reported the significant reduction in incidences of whitefly

(Bemisia tabaci), aphids and thrips, in protected crops by UV-blocking plastics

or nets when compared with UV- non blocking materials (Antignus et al. 1996 &

1998 & 2001, Antignus 2000).

Regarding the aspects discussed this thesis is divided in 4 more chapters. After

introduction (chapter 1), the major objectives of the chapter 2 were to study the

effects of various neem application methods (seed, foliar and soil drenching) at

various dose-rates on the colonization behavior, overall and individual fecundity,

immatures mortality and adult emergence of B. tabaci. In addition the efficacies

of each application method at various dose-rates were compared in relation to

potential use of neem in the humid tropics.

In chapter 3, the residual toxicity of the soil and foliar application of neem under

laboratory and greenhouse conditions were compared using the colonization

behavior, overall and individual fecundity, immatures mortality and adult


emergence of B. tabaci as dependent variables. Furthermore, residual toxicity

of application methods were compared in relation to their potential use in

protected cultivation.

A comparative study of neem with the two novel pesticides of microbial origin,

spinosad and abamectin is presented in the chapter 4. Studies were conducted

both in air conditioned, UV protected environments and under more open

conditions in net greenhouses to check for influences of the exposure

conditions on intensity and duration of residual activity. In addition, in no-choice

studies, toxicity of these novel pesticides were determined against various life

stages of the B. tabaci at different dose-rates and results were discussed in

context of their potential use in the humid tropics.

In the last chapter, chapter 5, immigration of three important sucking insect-

pests of tomatoes in lower Bangkok plains and related virus spread inside

greenhouses using different combinations of UV-blocking nets and plastics as

greenhouse cover were compared. Conditions of partial (partial ventilation) or

open access (complete ventilation) to the structures regulated by the doors

were tested to simulate different ventilation conditions. In addition, the

attractions of WF and thrips to the walls of the GH were also determined and

attempts were made to separate the thrips transmitted tospovirus and other

viruses in the experiments. All experiments were carried out in laboratories

(Entomological Laboratory 2; Whitefly Laboratory) and separately built

greenhouses constructed under the framework of the DFG Research group

FOR 431 entitled �Protected cultivation - an approach to sustainable vegetable

production in the humid tropics� at AIT campus during 2002-2005. They are part

of a larger study which aims to establish sustainable and environmentally

friendly vegetable production systems under protected cultivation in the humid

tropics.

Use of seed, foliar and soil treatments of Azadirachtin to control B. tabaci 13

Use of seed, foliar and soil treatments of Azadirachtin to control Sweetpotato Whitefly Bemisia tabaci (Hom.: Aleyrodidae) on tomato plants6

2.1 Introduction The WF, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) originates from

tropical and subtropical regions with a worldwide distribution as a serious pest

of open field vegetable production (Tropics, Sub-tropics and Mediterranean

regions) and crops grown under protected cultivation (Butler and Heneberry

1986, Denholm et al. 1996). WF has been recorded from over 600 different

plant species (Mound & Halsey 1978, Greathead 1986, Cock 1986, Secker et

al. 1998) and it causes damage to the tomatoes in many ways such as direct

sap feeding, virus transmission (Tomato Yellow Leaf Curl), sooty mould

(reduced cosmetic value of fruits and photosynthetic area of plant) and uneven

ripening of the fruits (Maynard and Cantliffe 1989, De Barro 1995, Rapisarda

and Garzia 2002).

Chemical control is the primary method to manage WF. However control with

pesticides is difficult for several reasons. Penetration of active ingredients after

topical treatments can be inhibited by the waxy shelters protecting the immobile

larval and pupal stages (James 2003) and all feeding stages colonize the

abaxial surface of leaves and spraying from the top of the canopy results in

incomplete coverage. Furthermore, shortly after immigration, typically all

developmental stages of WF are present on the plants (Prabhaker et al. 1989).

Thus, any control strategies not targeting all stages would be inefficient. This is

particularly relevant for the largely non-feeding pupal stages. Moreover, the

short and multiple life cycles with high reproduction rates, particularly under

tropical conditions, favors fast selection of resistant biotypes to different classes

of insecticides especially organophosphates, pyrethroids and cyclodiens. Even

for the relatively young group of chloro-nicotinyl insecticides (leading substance:

imidacloprid) resistant biotypes are already described (Prabhaker et al. 1989,

Cahill et al. 1995, Dittrich et al. 1990a & b, Byrne et al. 2003).

6 Part of this chapter was published as Effects of different application methods of azadirachtin against sweetpotato whitefly Bemisia tabaci Gennadius (Hom., Aleyrodidae) on tomato plants P. Kumar, H.-M. Poehling and C. Borgemeister. J. Appl. Entomol. 129 (9/10), 489�497.

2


Additionally, natural enemies, which can play an important role in the integrated

control of pest complexes particularly in protected environments, can be

seriously affected by pesticide treatments (e.g. Gonzalez-Zamora et. al. 2004).

Even neem products (see below), often claimed to be selective, can significantly

affect natural enemies such as E. formosa (Feldhege and Schmutterer 1993).

Azadirachtin, a steroid-like tetranortriterpenoid derived from neem trees

(Azadirachta indica Juss.), is a strong anti-feedent, repellent and growth

regulator for a wide variety of phytophagous insects, including WF (Coudriet et

al. 1985, Flint and Sparks 1989, Prabhaker et al. 1989, Schmutterer 1990, Liu

and Stansly 1995, Mitchell et al. 2004). The efficiency of neem against WF has

been tested in numerous experiments in field and greenhouse studies but with

variable success (Puri et al. 1994, Leskovar and Boales 1996, Akey and

Henneberry 1999). Main advantages of using so-called bio-pesticides like neem

are reduced human toxicity, fast and complete degradation in the environment,

low risk for resistance and sometimes selective properties concerning non-

target organism (Feng and Isman 1995, Immaraju 1998, Walter, 1999). Most

control strategies and related studies, however, focus on foliar applications of

neem products. The results are often unsatisfactory for several reasons such

as: side effects on natural enemies (Feldhege and Schmutterer 1993), rapid

photo-degradation and insufficient distribution within the crop canopy (Stokes

and Redfern 1982, Larew 1988, Barnby et al. 1989). Systemic distribution of

neem as recently described for thrips control (Thoeming et al. 2003) could help

to overcome these shortcomings, to improve the efficiency, and to enable

growers to achieve a higher level of reliability and sustainability in WF

management with neem. Moreover, it could be hypothesized that soil

application would strongly reduce the contamination of plant foraging

parasitoids or predators and would open the door for synergistic use of the bio-

pesticide (�fast task force�) and parasitoids or predators (�long term sustainable

control�).

A detailed comparison of application methods (topical vs. systemic) regarding

possible alterations in sensitivity of different developmental stages has not been

conducted to date. In order to test the assumptions listed above we undertook a

series of experiments under controlled conditions to measure the effects of

three different methods of neem treatment on the colonization, oviposition, as


well as egg hatch and mortality of immature stages of B. tabaci on tomato

plants. The experiments are part of a project aimed at developing a WF

management strategy for tomato production under protected cultivation in the

humid tropics.

2.2 Materials and Methods Location, host plant and rearing of whiteflies The study was part of an interdisciplinary research project funded by the

German Research Foundation (FOR 431) entitled �Protected cultivation - an

approach to sustainable vegetable production in the humid tropics�.

Experiments were conducted on tomato plants (Lycopersicon esculentum Mill

(Solanaceae), cv. King Kong II) at the greenhouse and laboratory complex

provided for the AIT-Hanover Project, Asian Institute of Technology, Bangkok,

Thailand. The initial whitefly culture was obtained from the DoA (Department of

Agriculture) Virology section, Chatuchak, Bangkok. This culture was maintained

on eggplant and cotton seedlings for the past 2 years without any pesticides.

Thereafter, the culture was mass reared in air conditioned rooms using the

above mentioned tomato variety. The plants were kept in insect-proof cages

(1.20 x 65 x 65 cm) at 24± 2°C and 60-70% relative humidity (rH). WF of the

same age, i.e. L1, L2 and adults, were obtained by allowing female, B. tabaci

(approximately 400 with a 1:1 male and female ratio) to lay eggs for 24 h on

caged tomato plants. Thereafter, adults were removed from the cages using an

aspirator. Plants with eggs were then stored in insect-proof cages for further

synchronized development of B. tabaci. Plants with L1, L2, L3 or pupae were

used for the neem experiments (see below) or kept until adult emergence in

order to obtain adults of similar age.

Neem Formulations

Two types of neem products, NeemAzal-U® (17% Azadirachtin A) and

NeemAzal®-TS (1% Azadirachtin A) (Trifolio M GmbH, Lahnau, Germany) were

used either in choice or no-choice tests. NeemAzal-U® was used for seed

soaking and soil drenching-experiments, whereas NeemAzal-TS® only for foliar

applications. Different concentrations of drenching solution were prepared by

dissolving 0.75 (Azadirachtin = 0.1275 g), 1.50 (Azadirachtin = 0.255 g), 2.25

(Azadirachtin = 0.3825 g) and 3.0 g (Azadirachtin = 0.51 g) NeemAzal-U® in 1


liter tap water, which was then shaken for 30 minutes on a mechanical shaker

before use. For foliar applications, 1 (0.01 g AZA), 3 (0.03 g AZA), 5 (0.05 g

AZA) 7 (0.07 g AZA) and 10 ml (0.1 g AZA)/NeemAzal T/S were dissolved in 1 l

tap water, and then shaken vigorously for approximately 10 min.

Before spraying, solutions were shaken again to ensure proper distribution of

the oil-based formulation in water. For spraying, a local hand-held water sprayer

of 1 l capacity was used. Control treatments were performed with a blank

formulation of 3.0g/l NeemAzal® -U or with tap water in the case of NeemAzal® -

T/S. Seeds were soaked in 50 ml of each dilution of NeemAzal®-U and pot

substrates were drenched with 50 ml of the NeemAzal®-U solutions. For foliar

spraying approximately 50 ml of NeemAzal® -T/S solutions were applied per

plant.

Treatments

All experiments described below were conducted on tomato plants cv. King

Kong II grown and/or planted in 10 cm diameter plastic pots with 180 g of local

substrate (pH-5.3; organic matter - 28%; sand - 30%; silt - 39%; clay - 31%;

total N - 0.4% ; K - 0.65%; P - 0.18%; Ca - 0.08%). Plants were kept in an air-

conditioned laboratory at 24± 2°C, 60-70% rH with a photoperiod of 16:8 h

(light: dark). Tomato plants were treated with the respective neem formulations

as described below with ten replications per treatment and trial and with three

repetitions over time.

Experiments

Seed Soaking

Tomato seeds were gently shaken in a Petri dish for 36 hours in 50 ml of 0.75,

1.5, 2.25 and 3.0 g NeemAzal®-U/l and 3.0 g blank /l formulation to ensure a

uniform soaking of neem. In a preliminary test, no negative effects of seed

soaking on germination were observed. Treated seeds were planted in pots and

kept for two weeks in a climate controlled environment. A total of 50 plants were

used in the experiment. Afterwards, plants were randomly placed in a

transparent acrylic box (1.2 m height, 75 cm width with 30 meshes net fixed at

the top and at two sides for proper ventilations and air circulations) for exposure

to WF. Approximately 400 same-aged adult WF (2-d old) were released into the

cages for 72 hours to allow adult WF sufficient time for choice of plants and

oviposition. Starting one day after the release for three consecutive days, all


adult WF per plant were counted to record the colonizing preference of WF.

Thereafter, adults were removed from the boxes and WF eggs on each leaflet

counted using a microscope. Plants were maintained in WF-free cages and

after 30 days when the majority of surviving WF had completed their

development plants were removed from the cages. Then the number of living

and dead immatures and empty pupal cases were counted to record adult

emergence and immature mortality. Immatures were considered dead when

they lost their normal yellow-green color, turgidity and smooth cuticle structure.

Soil treatment Choice Experiment

Soil treatments were carried out with the same blank and four neem solutions

as described for the seed soaking experiment. The substrate of two-week old

tomato plants was treated with 50 ml of the neem solutions. After a 48 hour

waiting period for uptake and translocation of neem ingredients plants were

exposed to WF. Further experimental details were similar to the seed-soaking

experiment.

No-choice experiments, stage specific sensitivity

Plants with different synchronized developmental stages of B. tabaci were

produced as described above. Once the WF reached the desired development

stage, numbers of larval instars and pupae were reduced to 50/plant with the

help of an entomological pin directed under a microscope. Only in the case of

eggs no adjustment was made and the number of eggs on each leaflet was

counted before treating the tomato plants. Each of the 50 individuals left was

marked for the purpose of easy counting and identification. Afterwards plants

were treated with 50 ml NeemAzalU solution /pot and 10 replications were run

for each treatment. Treated plants with eggs were stored until emergence of L1.

Six days later the numbers of hatched eggs were counted to record the

proportion of hatched individuals. In case of immatures, plant substrates were

treated 7 (L1), 10 (L2), 14 (L3) and 17 days (pupae) after egg laying. The

growth and development of WF development was monitored until adult

emergence. By counting the empty pupal cases, live and dead larva, mortality

and the proportion of hatched pupae could be calculated.


Foliar treatments

Choice experiments Potted tomato plants were sprayed with 1, 3, 5, 7 and 10 ml/l NeemAzalTS on

adaxial and abaxial leaf surfaces until runoff. Plants sprayed with tap water

alone served as controls. Afterwards, plants were exposed to WF and

subsequent maintenance was similar to that described for soil treatments. After

30 days of neem application (until emergence of all adults), dead immature and

empty pupal cases were counted to determine immature mortality.

No-choice experiments, stage specific sensitivity Different developmental stages of B. tabaci on tomato plants were established

as described above. NeemAzalTS was applied as foliar spray directly on the

adaxial and abaxial surfaces of leaves carrying desired stages of WF. Growth

and development were monitored until adult emergence followed by counting of

the proportion of empty pupal cases, dead and alive larvae to calculate mortality

rates.

Statistical analyses

Data with percentage egg hatching, percentage immature mortality and

percentage adult emergence were subjected to HOVTEST = LEVENE option of

SAS to account for homogeneity of variance and normality. In the case of non-

homogeneity, percent values were transformed using arcsine�square-root

(arcsine√) transformation. Insect count values were transformed by square-root

(√) transformation before running an ANOVA. (Steel and Torrie 1980, Gomez

and Gomez 1984). Data were analyzed using the PROC GLM procedure in

SAS (SAS, 1999). In case the ANOVA yielded significant F-values, means were

compared using Tukey�s HSD procedure unless mentioned otherwise. A

significance level of ∝ = 0.05 was used in all analyses.

2.3 Results Seed-Soaking experiments

The mean number of adults per plant, the number of laid eggs, the percentage

of hatched eggs and the mortality of immature WF on plants grown from neem

treated seeds are summarized in the table 2.1. Neem seed treatments with 2.25

and 3.0 g NeemAzal U /lw resulted in a significant and dose dependent

reduction in the number of adults that colonized the plants (F = 18.92; df = 4,


145; P<0.0001) and in the number of deposited eggs as well (F= 33.34; df = 4,

145; P<0.0001). However, no significant difference in individual fecundity (eggs

deposited per female) were observed (F = 2.06; df = 4, 145; P = 0.0885). WF

did not discriminate between plants grown from seeds treated with blank

formulation, 0.75 and 1.50 g NeemAzalU /l for egg deposition. With respect to

egg hatch a significant reduction by neem treatments could be observed (F =

119.90; df = 4, 145; P<0.0001) resulting in fewer immatures on the plants

treated with increasing neem concentrations (F = 373.53; df = 4, 145;

P<0.0001). Moreover, the mortality of immatures increased in relation to the

dosage of neem almost 3-fold, if plants from blank treated seeds were

compared with those treated with 3.0 g NeemAzalU/l.

Soil treatment

Choice Experiment

The mean number of adult WF and eggs per plant, percentage eggs hatched

and percent mortality on plants treated by soil application using different

concentrations of NeemAzal®U solutions are summarized in table 2.2.

NeemAzal®U significantly reduced plant colonization by adult WF (F = 500.33;

df = 4, 145; P < 0.0001) as well as the number of deposited eggs compared to

the blank treatment (F=334.64; df = 4, 145; P <0.0001). In contrast, the females

deposited more eggs on tomato plants treated with highest concentrations (2.25

and 3.0 g/l) of azadirachtin (F = 34.78; df = 4, 145; P <0.0001). Moreover, neem

significantly affected the percentage of hatched WF eggs (F = 1862.49; df = 4,

145; P<0.0001) and induced increasing immature mortality (F = 4946.55; df = 4,

145; P <0.0001) in dose dependent manner with significant differences between

treatments.


Table 2.1. Mean (±SE) number of adult whiteflies, total number of eggs deposited, % hatched eggs, % mortality of immature stages of Bemisia

tabaci on tomato plants with seeds treated with NeemAzal U or a blank solution (control).

Values in columns followed by same letters are not significantly different (Tukey�s HSD

test; P<0.05)

Table 2.2. Mean (±SE) number of adult whiteflies, total number of eggs deposited, % hatched eggs, % mortality of immature stages on tomato plants after treatment of substrate with NeemAzal U or a blank solution (control).


test; P<0.05)

No-choice experiments, stage specific sensitivity Significant differences between all treatments (F = 1066.56; df = 4, 145;

P<0.0001) could be observed for the percentage of eggs hatched (F = 1066.56;

df = 4, 145; P<0.0001) and for the mortality of L1 (F = 1223.93; df = 4, 145; P <

0.0001), L2 (F = 1888.34; df = 4, 145; P < 0.0001), L3 (F = 3932.93; df = 4, 145;

P<0.0001) and the pupal stage (F = 3932.93; df = 4, 145; P <0.05) (table2.3).

Neem concentrations No. adult No. eggs % eggs

hatched % Mortality

Blank 30.97± 0.60a 261.40± 6.27a 83.75± 0.32a 13.01±0.35a 0.75 g/l 30.20± 0.74a 260.23± 11.13a 78.18± 0.72b 23.16±0.31b 1.50 g/l 28.23± 1.07ab 246.20± 7.86a 75.73± 1.23bc 23.94±0.31c 2.25 g/l 25.93± 0.95b 206.53± 10.09b 75.03±0.29c 28.10±0.34c 3.0 g/l 21.20± 1.17c 147.77± 5.90c 62.93±0.34d 35.67±0.76d

Neem concentrations No. adult No. eggs % Eggs

hatched % Mortality

Blank 35.50± 0.79a 345.83±13.52a 93.26 ± 0.27a 10.09 ± 0.10a 0.75 g/l 24.73± 0.47b 169.46 ± 4.68b 72.11± 0.18b 52.15 ± 0.38b 1.50 g/l 17.71± 0.57c 144.13 ± 4.12c 62.20±0.22c 61.57 ± 0.29c 2.25 g/l 9.93± 0.38d 106.00±1.26d 54.74 ± 0.73d 73.69 ± 0.30d 3.0 g/l 6.86± 0.29e 90.36± 1.16e 51.40 ± 0.40e 91.59 ±0.49e


Again, regarding all stages, efficacy of neem increased with the concentration of

the applied solution. When comparing the reaction of the immature stages, L1

was obviously the most sensitive one.

Foliar treatments.

Choice experiments

Colonization behavior of adults was strongly affected by foliar treatments with

NeemAzal TS (F = 346.69; df = 5, 174; P<0.0001) (see table 2.4). Moreover,

significant differences were detected in the number of eggs deposited (F =

557.80; df = 5, 174; P<0.0001). The foliar treatment resulted in significantly less

eggs developing finally to the larval stage compared to the tap water treated

plants (F = 3590.31; df = 5, 174; P<0.0001). Similar to the soil application

fecundity per female WF increased at highest (7 & 10 ml/l) concentration of

NeemAzal TS tested in the experiment (F= 11.92; df= 5, 174; P<0.0001). It

could be observed that most developing L1 larvae (crawlers) died within the

eggshell immediately before or during hatching (7 �d after egg laying). Mortality

of immatures from neem treated plants was significantly different compared to

control treatments (F = 2053.47; df = 5, 174; P<0.0001), which resulted in a

fewer number of adults developing on these plants. The dose relation was

similar to the experiments described above.


Table 2.3. Mean (±SE) % hatched eggs, % mortality of larval stages (L1 – L3) and pupa on tomato plants with substrate treated with NeemAzalU after infestation with different synchronized developmental stages of B.

tabaci.

Values in columns followed by same letters are not significantly different (Tukey�s HSD test; P<0.05)

Table 2.4. Mean (±SE) number of adult whiteflies, total number of eggs deposited, % eggs hatched, % mortality of larvae and % emerged adults on tomato plants treated with foliar application of NeemAzal TS and water (control).

Values in columns followed by same letters are not significantly different (Tukey�s HSD test; P<0.05).

Neem concentrations % Eggs hatched

L1

L2

L3

Pupae Blank 92.56±0.35a 13.46±0.96a 14.26±0.72a 9.66± 0.40a 9.60±0.49a

0.75 g/l 73.87±0.28b 35.80±0.77b 32.26±0.85b 31.93± 0.20b 31.40±0.82b 1.50 g/l 65.21±0.84c 52.33±0.91c 47.80±0.37c 45.00±0.35c 40.33±0.28c 2.25 g/l 57.25±0.43d 71.66±0.68d 68.40±0.36d 65.86±0.49d 52.73±0.35d 3.0 g/l 54.25±0.32e 87.00±0.32e 83.93±0.72e 78.93±0.40e 73.73±0.70e

Neem concentrations No. adult No. eggs % eggs hatched % Mortality Water 39.40 ± 1.20a 286.53±9.01a 94.24 ± 0.21a 5.71 ± 0.17a 1 ml/l 26.90 ± 1.32b 247.86 ± 6.42b 71.90 ± 0.22b 63.54 ± 0.22b 3 ml/l 18.73± 0.51c 158.03 ± 3.48c 60.70 ± 0.29c 68.61 ± 0.46c 5 ml/l 11.86 ± 0.52d 102.03±1.65d 55.26 ± 0.27d 73.31 ± 0.90d 7 ml/l 7.73 ± 0.22e 83.76 ± 1.12e 49.35 ± 0.34e 86.06 ±0.52e

10 ml/l 5.23 ±0. 24f 53.63 ± 1.22f 43.26 ± 0.49f 93.47 ± 0.52f

Mortality (%)


No-choice experiments, stage specific sensitivity

The results of these experiments are summarized in the table 2.5. The foliar

treatment during the early egg stage of WF resulted in a significant lower

amount of eggs completing development to L1 (F = 4874.36; df = 5, 174;

P<0.0001) compared to the untreated control. Moreover, significant differences

in percent mortality were observed between control and foliar neem treatments

regarding L1 (F = 4288.40; df = 5, 174; P < 0.0001), L2 (F = 6471.62; df = 5,

174; P<0.0001) L3 (F = 10156.5; df = 5, 174; P<0.0001) and the pupal stage (F

= 5441.06; df = 5, 174; P<0.0001). The pupal stage was less susceptible

compared to all three larval stages of WF. The mortality of L1 and pupae

steadily increased with the neem concentration applied.

Table 2.5. Mean (±SE) % eggs hatched, % mortality of larval stages (L1 –L3) and pupa on tomato plants treated after infestation with different synchronized developmental stages of B. tabaci with foliar spraying of NeemAzal TS.


test; P<0.05)

Neem concentrations Egg hatch

L1

L2

L3 Pupa

Water 93.97±0.36a 9.80±0.51a 7.93±0.52a 7.400±0.43a 7.73±0.28a 1 ml 68.72±0.51b 72.53±0.52b 70.33±0.54b 69.53±0.33b 29.53±0.20b3 ml 64.86±0.39c 88.93±0.81c 81.20±0.34c 81.36±0.37c 51.00±0.35c5 ml 44.49±0.56d 97.06±0.18d 95.60±0.26d 95.46±0.23d 67.20±0.41d7 ml 17.57±0.49e 100.0±0.00e 100.00±0.00e 100.00±0.00e 69.73±0.29e

10 ml 11.26±0.50f 100.0±0.00e 100.00±0.00e 100.00±0.00e 81.73±0.28f

Mortality (%)


2.4 Discussion Plant choice and oviposition The choice experiments either with seed, soil or foliar application of NeemAzal,

demonstrated deterrent effects resulting in fewer adults settling on the treated

tomato plants compared to untreated controls. Moreover, this effect was clearly

dose dependent and particularly pronounced when a foliar application was

used. The observation of repellent effects of neem on adult WF corroborates

reports of Coudriet et al. (1985), Hilje et al. (2003) & Nardo et al. (1997) working

with Bemisia tabaci, and of Prabhaker et al. (1999) with B. argentifolii. Similar

results are also described for other pests attacking tomatoes such as the

leafminers, Liriomyza trifolii (Burgess) and L. sativae Blanchard (Webb et

al.1983), Spodoptera litura F. (Joshi and Sitaramaiah 1979) or even the locust

(Schistocerca gregaria) (Schmutterer 1985 & 1988). In addition to the

deterrence of adults we could observe lower deposition rates of eggs on all

treated plants independent of application method. The numbers of eggs laid

were especially low after treatments with higher neem concentrations. Reduced

oviposition is a normal consequence if adults try to avoid settling on a host

plant. In contrast, in soil and foliar treatment experiments, individual fecundity

per female was higher compared to the respective controls like in case of soil

application 19 eggs were deposited at control (blank) against 22 and 28 eggs

per female at dose-rates of 2.25 and 3.0 g/l NeemAzal U. Similarly individual

fecundity per female increased from 15 (control) to 22 at highest dose-rate

tested (10 ml/l of NeemAzal TS). Moreover, these differences were not so

apparent at other dose-rates tested in both experiments. No such effect was

detected in the case of seed-treatment experiment. The reason for the

increased fecundity is still unclear. It is possible that the lesser crowding on

these treatments reduces intra-specific competition; on the contrary, similar

effects attributed to sub-lethal insecticide stress effects are reported in Bemisia

by Dittrich et al. (1990 a&b). Furthermore, although not measured in our

experiments, a reduced uptake of phloem sap by adults avoiding feeding or

changing the feeding site may more frequently have resulted in reduced

numbers of ripened eggs ready for deposition. Our results are in agreement

with findings of other authors who have studied neem compounds or related

substances from Melia azadirach on B. tabaci (Coudriet et al. 1985, Nardo et al.


1997, Abou-Fakhr Hammad et al. 2001). The difference in the magnitude of

host preference alteration between the three application methods may be

related to the presence of different amounts of neem residues in or on the

leaves: foliar treatment should result in much higher amounts of active

ingredient on the leaf surface being directly encountered by the plant dwelling

adults compared to seed and soil treatments, where neem compounds are

translocated internally to the leaves. However, we could not differentiate in our

observations between adults reacting immediately after plant contact or after

first feeding (probing). In total, the clear feeding deterrent effects measured

indicate a very sensitive reaction of adults to select non-treated plants for

feeding.

Egg hatch All three treatment-methods influenced the maturing and hatching of larvae from

eggs deposited on the treated plants. The reduction was lowest in seed

treatments compared to the soil and foliar applications, which corroborates

earlier findings of Prabhaker et al. (1999) with B. argentifolii. Observation of the

process of hatching revealed that the apparent reduction in successful egg

hatch was due to neem on crawlers after eclosion from viable eggs when they

came into contact with neem residues on the plant leaves and on the egg

chorion. Hence, the reduction was not due to a disruption or inhibition of

embryogenesis. We suspect that residual activity of neem on the egg chorion

was toxic to the emerging crawlers as they were trying to come out from their

eggs shell. We observed several of such half-emerged dead crawlers (under

the microscope). These observations are similar to ones reported by von Elling

et al. (2002).

Mortality of immatures All three methods of neem treatment resulted in strong lethal effects on the

immatures. Consequently, on the treated plants, much lower numbers of WF

completed development to the adult stage. Direct effects after topical treatments

on a large number of insects and WF (see e.g. von Elling et al. 2002) are

reported and should not stay in focus here. More interesting are the strong

effects shown without direct application to the targets. The results indicate that

neem is efficiently absorbed through seeds or roots, transported via stems to

the leaves or absorbed by the leaves and distributed translaminar. It could be


also concluded, regarding the feeding habits of whiteflies, which active

compounds occur in the phloem vessels, the primary feeding site of WF.

Systemic activity of neem has been reported in several studies in different

herbivore-plant systems like in Tenthredinidae larvae (Keelberg 1992),

Colorado potato beetle Leptinotarsa decemlineata Say. (Col.: Chrysomelidae),

(Otto 1994) and larvae of Liriomyza huidobrensis Blanchard (Dipt.

Agromyzidae) (Weintraub and Horowitz 1997).

Only a few earlier studies have used the active uptake by non-manipulated

seeds or roots, rather than the artificial loading of plants by immersion of cut

stems or leaves in neem solution. Our results are in agreement with earlier

findings of Prabhaker et al. (1999) with B. Argentifolii, Thoeming et al. (2003)

and Ossiewatsch (2000) with western flower thrips, Frankliniella occidentalis

and Larew�s (1986 and 1988) studies with aphids. All these studies showed

systemic translocation of neem after treatment of bottom parts of intact plants

resulting in strong effects on these sucking insects. Furthermore, with insect-

pests having different feeding habits, such as the leafminer Liriomyza trifollii,

seed treatments with neem showed similar systemic properties in ornamental

plants (Larew et al.1985).

Effects of foliar application and stage specific mortality Our results indicate that all three larval stages of B. tabaci are highly

susceptible to the foliar treatment with neem. The L1 was most susceptible

compared to L2 and L3. The pupal stage was least susceptible compared to all

three larval stages. This could be due to the fact that the pupal stage is a largely

non-feeding stage, where feeding occurs only in the first part of the

development (Gill 1990). Additionally, due to the presence of thick cuticular

layers it avoids any chance of contact toxicity. These results agree with earlier

findings of Coudriet et al. (1985), Lindquist and Casey (1990), Price and

Schuster (1991).

The different intensity of WF reaction to foliar sprays compared to seed and soil

treatments supported findings of Liu and Stansly (1995), who found similar

differences in nymphal mortality of B. tabaci comparing a spray and leaf-dip

method for treatments with the neem product Margosan-O (Grace Grace-Sierra

Horticultural Products Company, Fogelsville, PA).


Conclusion

Neem as a natural botanical pesticide with a low risk of toxicity to humans and

animals could be one important plant protection agent in IPM programs. The

results presented here show that neem is systemically translocated in tomato

plants, and that this feature is of paramount importance for the control of plant

sucking insects including WF. In particular, immatures of B. tabaci are highly

susceptible to neem if the compound is allowed to be translocated systemically.

The use of neem as a systemic pesticide has advantages in protected

cultivation, i.e. where plants can be grown in pots or on artificial substrates; and

where the infection pressure can be reduced by the use of mechanical barriers

such as nets.

Making use of the systemic properties of neem can help to overcome two major

drawbacks of neem if used for canopy spraying: fast degradation because of

strong ultra-violet light (Johnson et al. 2003) and deleterious side effects on

beneficial non-target organisms. However, concerning the latter point, more

detailed studies in tropical greenhouses are needed to determine the possible

side effects of neem on the indigenous or released natural enemy communities

of Bemisia tabaci. These largely comprise Aphelenidae parasitoids and some

general predators. Further studies by our group will focus on using these

findings on the systemic properties of neem to improve complex pest �

beneficial communities for better management of Bemisia in humid tropics.

Persistence of Azadirachtin against B. tabaci in Lab and GH 28

Persistence of soil and foliar azadirachtin treatments to control Sweetpotato Whitefly Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) on tomatoes under controlled (laboratory) and field (netted greenhouse) conditions in the humid tropics7

3.1 Introduction The WF, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) is a polyphagous

pest feeding on over 600 plant species worldwide (Mound & Halsey 1978,

Greathead 1986, Cock 1986, Secker et al. 1998). Tomatoes grown both in

temperate and tropical regions, under protected cultivation, are highly

vulnerable to whitefly damage (Butler and Heneberry 1986, Denholm et al.

1996). The pest status of this species is due to a number of factors: high degree

of polyphagy, ingestion of phloem sap, massive honey dew secretion that

reduces both the cosmetic value of the tomato and the available leaf area for

photosynthetic activities, uneven ripening in tomatoes and transmission of plant

viruses like TYLCV (Duffus 1987, Maynard and Cantliffe 1989, Byrne et al.

1990, De Barro 1995, Rapisarda and Garzia, 2002).

Chemical control is the primary method for managing WF. However, the use of

chemicals has been inadequate principally because of the rapid emergence of

resistance to different classes of insecticides, especially organophosphates,

pyrethroids and cyclodienes. Even for the relatively new group of chloro-

nicotinyl insecticides (leading substance imidacloprid) resistant biotypes have

been described (Prabhaker et al. 1989, Dittrich et al. 1990a, Cahill et al. 1995,

Byrne et al. 2003).

Alternatively, certain chemicals, derived either from plants or from certain micro-

organisms, which we term here as biopesticides have been promoted in recent

years. These include especially the azadirachtins, as well as avermectins and

spinosyns. Azadirachtin, a steroid-like tetranortriterpenoid derived from the

neem tree (Azadirachta indica Juss.), acts as a strong anti-feedent, repellent

and growth regulator for a wide variety of phytophagous insects, including WF

(Coudriet et al. 1985, Schmutterer 1990). It delays and prevents moulting,

7To be published as Kumar, P., and H-M. Poehling. Persistence of soil and foliar azadirachtin treatments to control Sweetpotato Whitefly Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) on tomatoes under controlled (laboratory) and field (netted greenhouse) conditions in the humid tropics. Submitted to Journal of Pest Sciences.

3


reduces growth, development and oviposition; and can cause high mortality,

particularly in immatures, as documented for a wide group of phytophagous

insects including WF (Coudriet et al. 1985, Flint and Sparks 1989, Prabhaker et

al. 1989, Schmutterer 1990, Liu and Stansly 1995, Mitchell et al. 2004, Kumar

et al. 2005). Neem products have been developed to address many pest

problems, and are registered in many countries. Local production in most

countries in the humid tropics makes them economic and readily available for

smallholders.

The major problem with neem products based on triterpenoids as the active

ingredient is the rapid photo-degradation by UV radiation when applied to the

crop canopy as a foliar application (Pradhan and Jotwani 1968, Stokes and

Redfern 1982, Saxena et al. 1982, Meisner et al. 1982, Hellap 1984, Barnaby et

al. 1989, Caboni et al. 2002, Johnson et al. 2003, Barrek et al. 2004). Soil

treatments making use of the systemic properties of azadirachtin (Thoeming et

al. 2003, Kumar et al. 2005) may lessen instability and prolong persistency of

the products.

A detailed comparison of persistency under different application methods

(systemic, and topical) would help in choosing the optimal method and

application frequencies to improve the overall neem use efficiency, and enable

the growers to achieve a higher level of reliability and sustainability in WF

management. Additionally, neem used for soil drenching would largely reduce

direct toxicity to plant-foraging natural enemies such as parasitoids, thereby

allowing its effective use as a component in IPM strategies.

This paper describes experiments to evaluate the persistence of different

application methods, optimal product concentrations and timing of application

for two commercial neem products in two environmental situations: climate-

controlled rearing rooms (air conditioned and artificially illuminated, i.e., with

intermediate temperature and low UV) and netted tropical greenhouses (high

temperature and high UV). Impacts on WF investigated included: colonization

preference, oviposition, eggs hatch and immature mortality.


3.2. Materials and Methods Location, host plant and rearing of whiteflies The study was part of an interdisciplinary research project funded by the




(Solanaceae), cv. King Kong II) at the greenhouse and laboratory complex of

the AIT-Hanover Project, Asian Institute of Technology, Bangkok, Thailand. The

initial WF culture was obtained from the Department of Agriculture Virology

section, Chatuchak, Bangkok and mass reared using insect-proof cages (1.20 x

65 x 65 cm) in air conditioned rooms (at 24± 2°C and 60-70% relative humidity

(rH)) on the above mentioned tomato variety. WF of the same age were

obtained by allowing female B. tabaci (approximately 400 with a 1:1 male and

female ratio) to oviposit for 24 h on caged tomato plants. Thereafter, adults

were removed and plants with eggs stored in insect-proof cages for further

synchronized development. The laboratory experiments were carried out in an air-conditioned laboratory

(24- 25ºC; rH 65-75%, photoperiod 16: 8 [light: dark], whereas the greenhouse

experiments were performed in two identical greenhouses (6x3x3 meters:72

mesh size, Econet®; Ludvig Swensoon, Sweden) at temperature range of 29-

39ºC; rH 55-75% and natural photoperiod. During the experimental period, daily

UV-A and temperature were measured with a Radiometer UV-Sensor (Dr.

Grobel UV-Elektronik GmbH, Germany) and thermometer respectively inside

greenhouse and in the laboratory. The measured mean UV-A for GH was in the

range of 15-16.0 w/m2, whereas it was 0.6-1.0 w/m2 in the laboratory during the

period of the experiments.

Neem Formulations

Two types of neem, NeemAzal-U® (17% Azadirachtin A) and NeemAzal-TS®

(1% Azadirachtin A) (Trifolio M GmbH, Lahnau, Germany) were used in

bioassays as choice tests. NeemAzal®-U formulated as powder for water-based

solutions was used for soil drenching experiments, whereas the NeemAzal®-TS,

formulated as liquid product with a high content of oil, was used for foliar

applications.


Different concentrations of drenching solution were prepared by dissolving 0.75

(Azadirachtin = 0.1275 g), 1.5 (Azadirachtin = 0.255 g), 2.25 (Azadirachtin =

0.3825 g) and 3.0 g (Azadirachtin = 0.51 g) NeemAzal-U® in 1 liter tap water,

which was then shaken for 30 minutes on a mechanical shaker (Orbit shaker,

Edmund Buhler Co., Dreieich, Germany) before use. For foliar applications 1, 3,

5, 7 and 10.0 ml NeemAzalT/S® /liter water were dissolved in tap water,

followed by a vigorous shaking for approximately 10 minutes. Before spraying,

solutions were shaken again to ensure proper distribution of the oil-based

formulation in water. A local hand-held sprayer of 1 l capacity was used. In the

case of NeemAzal-U®, 3.0g/l blank formulation of NeemAzal®-U (Trifolio-M,

GmbH, Lahnau, Germany) was used as a control, while in the case of

NeemAzal®-T/S tap water was used as a control. Pot substrates were drenched

with 50 ml of the NeemAzal®-U solutions. For foliar spray, approximately 50 ml

of suspension were sprayed until run off.

Treatments

All choice experiments were conducted on tomato plants cv. King Kong II grown

and/or planted in 10 cm diameter plastic pots with 180 gram of local substrate

(pH-5.3; Organic matter - 28%; Sand - 30%; Silt - 39%; Clay - 31%; Total N -

0.4%; K - 0.65%; P - 0.18%; Ca - 0.08%). Plants were either kept in an air

conditioned laboratory or under GH conditions as discussed above. Tomato

plants were treated with the respective neem formulations as described below

with eight replications per treatment per trial, and three replication trials over

time.

Experiments

1. Persistency of soil treatment with NeemAzalU

A. Greenhouse (GH) Soil treatments were carried out with 0.75, 1.5, 2.25 and 3.0 g Neem-Azal®-

U/lw and tap water as control. Each potted tomato plant was drenched with 50

ml neem at 7, 5, 3, and 1 day prior to introducing WF. Afterwards, plants were

arranged for a choice test in 8 replications in eight separate well ventilated

acrylic boxes (1.2 m height, 75 cm width; top and sides 72 mesh nets)

containing one plant of each treatment in a randomized block design and

exposed to WF under prevailing greenhouse (GH) conditions. Approximately

400 same-aged (1:1 male and female approximately) adult WF (2-d old) were


aspirated and released into the cages for 72 h to give adult WF sufficient time

for plant choice and oviposition. Starting one day after the release for three

consecutive days, all adult WF per plant were counted, and then returned, to

record the colonizing preference of WF. Thereafter, WF adults were removed

from the boxes and WF eggs on each leaflet counted using a microscope.

Plants carrying WF eggs were marked and placed inside a WF-free GH to allow

juveniles to develop. After 30 days, plants were removed from the GH and the

number of living and dead immatures and empty pupal cases were counted to

record adult emergence and mortality amongst immatures. Immatures were

considered dead if they had lost their normal yellow-green color, turgidity and

smooth cuticle structure. Three times per day water losses from the soil were

replenished, but without any drainage from the pots, to maintain optimum

moisture during the period of experiments.

B. Air conditioned laboratory Similar experiment as in A. was conducted but with treated plants kept under

laboratory conditions, as described above.

2. Persistency of foliar treatments of NeemAzalTS

A. Greenhouse

Potted tomato plants were sprayed with 1, 3, 5, 7 and 10 ml/l Neem-Azal T/S®

on adaxial and abaxial leaf surface until runoff at 7, 5, 3, and 1- day prior to

introducing WF. Plants sprayed with tap-water alone served as controls.

Thereafter, the arrangements of plants, exposure to the WF, maintenance of

tomato plants carrying WF eggs and data evaluation were carried out similar to

the above described soil drenching experiment (experiment 1).

B. Air conditioned laboratory Similar experiment as in A was conducted with treated plants kept under

laboratory conditions described above.

Statistical Analyses

Data with percentage egg hatching, immature mortality were subjected to

HOVTEST = LEVENE option of SAS to account for homogeneity of variance

and normality. In the case of non-homogeneity, percent values were

transformed using arcsine�square-root (arcsine√) transformation. Insect and

eggs count values were transformed by square-root (√) transformation before

running an ANOVA (Steel and Torrie 1980, Gomez and Gomez 1984). Data


were analyzed using the PROC GLM procedure in SAS to determine single or

interaction effects of factors (SAS 1999). Whenever significant interaction was

observed between factors, the level of one factor was compared to each level of

the other factor by all pair-wise multiple comparison procedures (Tukey�s test)

unless mentioned otherwise. All data are presented as Mean± SE. A significant

level of ∝ = 0.05 was used for all analyses.

3.3. Results 1. Persistency of soil treatment with NeemAzalU

A. Greenhouse (GH)

The interaction of the factors i.e. dose-rate* day was found significant for all

variables studied in the experiment i.e., adult colonization (F = 19.051; df = 12,

479; P<0.0001); egg deposition (F = 12.367; df = 12, 479; P<0.0001); egg hatch

(F = 17.52; df = 12, 479; P<0.0001); eggs laid per female (F = 3.805; df = 12,

479; P<0.0001) and immatures mortality (F = 62.39; df = 12, 479; P<0.0001).

The dose-rate was found to have significant effect on all variables, i.e., adult

colonization (F = 285.556; df = 4, 479; P<0.0001); egg deposition (F = 257.662;

df = 4, 479; P<0.0001); eggs laid per female (F = 5.427; df = 4, 479;

P<0.0001);egg hatch (F = 235.588; df = 4, 479; P<0.0001) and immatures

mortality (F = 2191.559; df = 4, 479; P<0.0001). The reduced persistency of

NeemAzalU with time was apparent with all parameters measured i.e. adult

colonization i.e., adult colonization (F = 158.607; 3, 479; P<0.0001); egg

deposition (F = 89.207; df = 3, 479; P<0.0001); eggs laid per female (F =

10.788; 3, 479; P<0.0001); egg hatch (F = 180.451; 3, 479; P<0.0001) and

immatures mortality (F = 941.200; 3, 479; P<0.0001).

The mean number of adult colonization, total eggs deposited, and eggs

deposited per female on the plants as well as the number of eggs hatched and

the immature mortality across the dose-rates and days are summarized in

tables 3.1, 3.2, 3.3, 3.4 and 3.5 respectively. The soil treatment reduced

colonization, egg deposition and egg hatch rate and caused mortality amongst

immatures. Moreover, higher individual fecundity was recorded which gradually

reduced over time. For instance, 25 eggs/female on 7-d reduced to 20

eggs/level (level of control) on day 5. However, at low dose-rates (0.75 and 1.5

g/l) persistence of effects rapidly decreased compared to the dose rate of 2.25


and 3.0 g/l, which remain highly effective until the 7-d post application. For

instance, the mortality of immatures with 3.0 g/l was reduced to almost half (88

% on 1-d and 45 on 7-d), whereas with 0.75 g/l already control levels were

reached at day 7.

Table 3.1. Mean (±SE) numbers of WF adult on tomato plant untreated and treated with neem applied to the soil across the different residue level and dose-rates of NeemAzal®-U under laboratory and in greenhouse conditions

Mean (±SE) total number of adult Residue age, days NeemAzal® -U

(g/l) 1-d 3-d 5-d 7-d Laboratory

Blank 24.46±0.55aA 25.50±0.61aA 24.00±0.37aA 25.96±0.84aA 0.75 19.04±0.42bA 22.58±0.47bB 24.88±0.64aB 24.04±0.53aB 1.50 20.00±0.43bA 22.88±0.58bB 24.50±0.58aB 24.25±0.35aB 2.25 11.38±0.42cA 12.33±0.59cA 17.17±0.64bB 19.63±1.20bB 3.0 8.71±0.20dA 10.58±0.44cB 13.75±0.47cC 17.13±0.56bD

Greenhouse Blank = 0 26.29±0.73aA 25.17±0.41aA 25.75±0.41aA 25.50±0.77aA

0.75 19.88±0.66bA 22.96±0.42bB 25.79±0.82aC 25.79±0.83aC 1.50 20.17±0.42bA 23.67±0.34bB 25.46±0.79aBC 26.75±0.79aC 2.25 14.13±0.19cA 15.08±0.33cA 19.63±0.50bB 22.42±0.39bC 3.0 10.96±0.39dA 12.67±0.34dB 18.96±0.40bC 21.13±0.31bD

Means followed by the same case small letters within column and upper case letters

within the row are not significantly different (P = 0.05, Tukey�s multiple comparison test

[SAS Institute 1999]. Data were subjected to square root transformation before the

analysis; non-transformed data on mean number of adult colonized tomato plants are

presented in the table.


Table 3.2. Mean (±SE) numbers of deposited eggs on tomato plant untreated and treated with neem applied to the soil across the different residue level and dose-rates of NeemAzal®-U under laboratory and in greenhouse conditions.




analysis; non-transformed data on mean number of total deposited eggs are presented

in the table.

Mean (±SE) total numbers of egg deposition Residue age, days NeemAzal® -U

(g/l) 1-d 3-d 5-d 7-d

Laboratory Blank = 0 250.92±3.56aA 249.38±2.96aA 248.38±4.07aA 253.63±4.76aA

0.75 197.92±3.28bA 224.71±2.59aA 245.33±2.13aB 240.46±3.64aB 1.50 196.88±3.38bA 222.58±2.55aB 240.79±4.61aB 241.00±3.32aB 2.25 141.79±3.50cA 127.83±6.79bB 168.21±3.99bC 179.08±9.69bC 3.0 116.33±3.76dA 125.71±4.93bA 141.17±4.41cB 166.63±3.70bC


0.75 200.17±1.86bA 236.92±3.46bB 263.25±4.10aC 262.88±6.46aC 1.50 200.50±3.29bA 235.96±3.64bB 251.71±2.86aB 252.42±10.79aB2.25 168.71±8.53cA 164.04±3.03cA 191.29±2.73bB 222.13±3.61bC 3.0 141.17±5.58dA 139.67±4.10dA 188.08±3.56cB 206.25±2.85bC


Table 3.3. Mean (±SE) numbers of deposited eggs per female on tomato plant untreated and treated with neem applied to the soil across the different residue level and dose-rates of NeemAzal®-U under laboratory and in greenhouse conditions.




analysis; non-transformed data on mean number deposited eggs per female are


Mean (±SE) number of eggs/female (Residue age, days NeemAzal® -U


Blank 20.70±0.45aA 19.74±0.39aA 20.80±0.45aA 19.95±0.68aA 0.75 20.96±0.46aA 20.12±0.53aA 20.00±0.50aA 20.01±0.46aA 1.50 19.92±0.57aA 19.71±0.50aA 19.78±0.36aA 19.97±0.39aA 2.25 25.54±0.94bA 20.96±0.98aB 20.12±0.76aB 19.70±1.50aB 3.0 26.96±1.00bA 24.02±0.79bB 20.89±0.78aC 19.95±0.84aC


0.75 20.60±0.64aA 20.85±0.60aA 20.83±0.65aA 20.82±0.82aA 1.50 20.02±0.40aA 20.09±0.33aA 20.34±0.91aA 19.51±0.93aA 2.25 23.74±0.98bA 21.94±0.57aA 19.85±0.66aB 19.91±0.38aB 3.0 25.78±0.54bA 22.26±0.69aB 20.00±0.48aC 19.60±0.33aC


Table 3.4. Mean (±SE) percentage eggs hatching on tomato plant untreated and treated with neem applied to the soil across the different residue level and dose-rates of NeemAzal®-U under laboratory and in greenhouse conditions.



[SAS Institute 1999]). Data were subjected to arcsine�square-root (arcsine√)

transformation before the analysis; non-transformed data on mean percentage eggs

hatching are presented in the table.

B. Laboratory

The interaction of the factors i.e. dose-rate*day was found significant for all

variables studied in the experiment i.e. adult colonization (F = 10.253; df = 12,

479; P<0.0001); egg deposition (F = 7.480; df = 12, 479; P<0.0001); eggs laid

per female (F = 5.057; df = 12, 479; P<0.0001 egg hatch (F = 9.464; df = 12,

479; P<0.0001;) and immatures mortality (F = 42.217; df = 12, 479; P<0.0001).

The dose-rate of neem had significant effect on all variables, i.e., adult

colonization (F = 349.383; df = 4, 479; P<0.0001); egg deposition (F = 439.417;

df = 4, 479; P<0.0001); eggs laid per female (F =12.310 ; df = df = 4, 479;

P<0.0001 ); egg hatch (F = 375.683; df = 4, 479; P<0.0001) and immatures

mortality (F = 1792.576; df = 4, 479; P<0.0001). Whereas the persistency of

neem reduced over time i.e. adult colonization (F =86.418; df = 3,479;

P<0.0001); egg deposition (F = 59.041; df = 3,479; P<0.0001); eggs laid per

Mean (±SE) % egg hatching, Residue age, days NeemAzal® -U


Blank = 0 95.74±0.64aA 95.07±1.97aA 95.57±1.20aA 96.44±1.15aA 0.75 72.52±1.79bA 77.30±1.09bA 85.81±0.79bB 94.17±1.93aC 1.50 63.75±0.81cA 69.13±0.66cA 78.09±0.85cb 89.14±1.80bC 2.25 56.51±0.85cdA 63.27±0.81cdA 74.15±0.74cdB 79.71±1.40cC 3.0 52.80±1.29dA 59.72±0.61dA 67.77±0.89dB 72.85±1.33cB


0.75 71.88±2.14bA 79.64±0.93bB 95.87±1.49aC 95.42±1.21aC 1.50 62.15±2.71cA 70.15±1.92cB 82.74±0.72bC 93.79±1.97aD 2.25 55.90±1.61cdA 69.84±1.11cB 79.53±1.11bcC 86.33±0.74bD 3.0 50.49±1.22dA 63.62±0.50cB 72.49±1.66cC 81.89±1.07bD


female (F = 17.237; df = df = 3,479; P<0.0001); egg hatch (F = 151.995; df =

3,479; P<0.0001) and mortality amongst immatures (F = 489.698; df = 3,479;

P<0.0001).

Table 3.5. Mean (±SE) percentage immatures mortality on tomato plant untreated and treated with neem applied to the soil across the different residue level and dose-rates of NeemAzal®-U under laboratory and in greenhouse conditions.

Mean (±SE) % immatures mortality Residue age, days NeemAzal® -U


Blank = 0 5.42±0.57aA 5.15±1.02aA 5.99±0.83aA 5.64±1.10aA 0.75 48.52±1.60bA 40.55±0.59bB 23.92±0.33bC 4.65±1.08aA 1.50 59.95±1.49cA 52.70±1.06cB 34.93±1.36cC 20.85±1.51bD 2.25 71.31±0.88dA 64.11±0.98dB 46.01±1.94dC 37.17±0.71cD 3.0 90.16±0.73eA 83.27±0.69eB 67.04±1.60eC 64.39±1.96dC


0.75 45.02±0.91bA 39.20±0.71bB 18.49±0.86bC 5.92±0.88aD 1.50 57.13±1.25cA 49.59±1.50cB 31.62±0.69cC 13.75±0.43bD 2.25 71.81±0.75dA 67.68±1.10dA 39.05±1.70dB 27.93±0.52cC 3.0 88.18±0.97eA 84.39±1.26eB 69.36±1.24eC 45.22±1.86dD



[SAS Institute 1999]). Data were subjected to arcsine�square-root (arcsine√)

transformation before the analysis; non-transformed data on mean percentages

immatures mortalities are presented in the table.

The mean number of plant colonization by adults, total, egg deposition, eggs

deposition per female, percentages of eggs hatch and immatures mortality

across the dose-rates and days are summarized in tables 3.1, 3.2 , 3.3, 3.4 and

3.5 respectively. The results indicate the stronger persistence of neem, when

applied as a soil drench under laboratory conditions compared with GH

conditions. This effect is expressed through: reduced colonization (from 8 WF to

17 WF at 1 and 7-d post application) and egg deposition (116 to 166 eggs at 1

and 7-day post application respectively). A higher individual fecundity from 1-

until 3-d post application at 3.0g/l (22 and 24 eggs/female under GH and

laboratory conditions respectively) were recorded, which reduced to the level of


controls 5-d post-application. Similarly, the dose rate of 2.25 and 3.0 g/l

remained effective until the 7-d post�application, e.g. the immatures mortality

was reduced from 90 to 64%; indicating a slower dissipation rate of applied

neem under laboratory conditions.

2. Persistency of foliar treatments of NeemAzalTS

A. Greenhouse The interaction of the factors i.e. dose-rate* day was found significant for all

variables studied in the experiment i.e., adult colonization (F = 72.051; df = 15,

575; P<0.0001); egg deposition (F = 50.026; df = 15, 575; P<0.0001); eggs laid

per female (F = 6.326; df = 15, 575; P<0.0001) egg hatch (F = 117.309; df = 15,

575; P<0.0001) and immatures mortality (F = 237.687; df = 15, 575; P<0.0001).

The effect of dose-rate significantly affected all variables compared to their

respective controls, i.e., adult colonization (F = 374.534; df = 5, 575; P<0.0001);

egg deposition (F = 255.732; df = 5, 575; P<0.0001); eggs laid per female (F =

17.321; df = df = 5, 575; P<0.0001); egg hatch (F = 699.199; df = 5, 575;

P<0.0001) and immatures mortality (F = 896.699; df = 5, 575; P<0.0001).

Whereas the persistency of neem reduced over the time and affected all studied

variables in the experiment i.e., adult colonization (F = 958.780; df = 3, 575;

P<0.0001); egg deposition (F = 730.210; df = df = 3, 575; P<0.0001); eggs laid

per female (F = 20.437; df = df = 3, 575; P<0.0001 );egg hatch (F = 1814.920;

df = 3, 575; P<0.0001) and immatures mortality (F = 4176.632; df = 3, 575;

P<0.0001). The mean number of adult colonization, total egg deposition, eggs

deposition per female, eggs hatch and immatures mortality across the dose-

rates and day are summarized in tables 3.6, 3.7, 3.8, 3.9 and 3.10 respectively.


Table 3.6. Mean (±SE) numbers of adults colonization on tomato plant untreated and treated with foliar application of neem across the different residue levels and dose-rates of NeemAzal®-T/S under laboratory and in greenhouse conditions

Mean (±SE) number of adult Residue age, days NeemAzal®-

T/S (ml/l) 1-d 3-d 5-d 7-d Laboratory

Control = 0 36.88±1.23aA 36.86±0.56aA 35.74±0.41aA 36.21±0.59aA1 22.52±1.63bA 31.71±0.59bB 33.42±0.45aB 35.79±0.45aC3 17.97±0.43cA 21.80±0.41cB 29.13±0.75bC 35.21±0.48aD5 12.72±0.75dA 21.58±0.50cB 21.75±0.55cB 33.79±0.75aC7 7.08±0.17eA 12.04±0.19dB 17.10±0.70dC 24.33±0.44bD

10 6.09±0.30eA 10.71±0.20dB 13.13±0.54eC 20.75±0.56cDGreenhouse

Control = 0 35.67±0.76aA 36.08±0.88aA 36.09±1.18aA 35.38±0.59aA1 24.07±0.69bA 29.50±0.71bB 35.96±1.16aC 35.33±0.74aC3 16.32±0.36cA 28.45±1.32bB 35.54±0.90aC 35.25±0.78aC5 11.22±0.35dA 20.13±0.62cB 34.13±0.82aC 35.25±0.92aC7 7.19±0.29eA 14.21±0.42dB 25.04±0.73bC 35.46±0.54aD

10 6.31±0.27eA 13.71±0.61dB 22.33±0.52bC 35.42±0.95aD Means followed by the same case small letters within column and upper case letters



analysis; non-transformed data on mean number of adults colonized tomato plants are



Table 3.7. Mean (±SE) numbers of deposited eggs on tomato plant untreated and treated with foliar application of neem across the different residue levels and dose-rates of NeemAzal®-T/S under laboratory and in greenhouse conditions




analysis; non-transformed data on mean number of deposited eggs are presented in

the table.

Neem applied through foliar application exhibited the persistency effect for

several days under GH conditions only at the higher rates of 7.0 and 10.0 ml/l.

Neem applied at other dose-rates at 3-d post application largely became

ineffective e.g. 6-7 adults WF colonized plants 1-d post application and after 5-d

there was no sig. difference observed in any tested dose-rates. Similarly, more

eggs were laid with lapse of time, for instance 304 eggs were deposited on 7-d

post application against 75 eggs on 1-d post application at 10.0 ml/l. Similar to

the soil application, the female WF deposited more eggs on plants with fresh

residue, which quickly came down to the level of the control e.g. 27 eggs at

10.0ml/l on 1-d post application against 17 eggs (similar sig. level of control) on

5-d post application. The result clearly indicates faster dissipation of the applied

neem through foliar application over soil drenching.

Mean (±SE) number of total deposited eggs Residue age, days NeemAzal®-

T/S (ml/l) 1-d 3-d 5-d 7-d Laboratory

Control = 0 312.75±9.50aA 316.67±4.00aA 315.46±4.30aA 312.58±5.17aA1 182.67±6.70bA 271.08±4.27bB 284.88±4.81bB 313.58±6.32aC3 152.63±3.59cA 191.17±3.29cB 247.08±6.18cC 311.50±5.94aD5 139.42±7.32cA 183.50±4.24cB 185.25±3.79dB 285.88±5.08bC7 83.38±2.12dA 133.88±2.14dB 191.29±7.34dC 209.33±4.34cD

10 81.92±3.41dA 128.92±3.39dB 153.67±.44eC 177.00±5.54dDGreenhouse

Control = 0 303.00±6.76aA 308.92±6.59aA 307.00±8.08aA 301.79±5.37aA1 207.42±7.61bA 255.04±12.51bB 305.00±8.81aC 303.75±6.02aC3 139.58±5.64cA 235.79±9.57bB 302.67±7.36aC 304.92±4.98aC5 106.67±2.08dA 166.75±6.36cB 281.46±4.52aC 309.58±8.54aC7 76.46±3.60eA 138.50±3.86dB 217.33±6.50bC 305.67±5.42aD

10 75.38±4.04eA 134.54±3.80dB 195.71±4.41bC 304.04±7.67aD


Table 3.8. Mean (±SE) numbers of deposited eggs per female on tomato plant untreated and treated with foliar application of neem across the different residue levels and dose-rates of NeemAzal®-T/S under laboratory and in greenhouse conditions




analysis; non-transformed data on mean number deposited eggs per female are


Mean (±SE) number eggs/female

Residue age, days

NeemAzal®- T/S

(ml/l) 1-d 3-d 5-d 7-d

Laboratory Control = 0 17.04±0.24aA 17.24±0.19aA 17.67±0.23aA 17.28±0.19aA

1 17.79±1.11aA 17.19±0.33aA 17.06±0.21aA 17.58±0.41aA 3 16.92±0.10aA 17.74±0.54aA 17.04±0.30aA 17.69±0.23aA 5 22.15±0.32bA 17.05±0.26aB 17.12±0.26aB 17.01±0.25aB 7 23.64±0.51bA 22.32±0.42bB 22.55±0.50bB 17.24±0.26aC

10 27.41±0.70cA 24.17±0.61bB 23.82±0.62bB 17.10±0.35aC Greenhouse Control = 0 17.02±0.23aA 17.27±0.45aA 17.20±0.43aA 17.07±0.14aA

1 17.44±0.72aA 17.27±0.68aA 17.04±0.22aA 17.24±0.27aA 3 17.16±0.67aA 16.76±0.29aA 17.12±0.33aA 17.39±0.29aA 5 19.53±0.83bA 16.61±0.41aB 16.65±0.38aB 17.58±0.21aB 7 21.58±0.87cA 19.60±0.38bA 17.38±0.19aB 17.25±0.19aB

10 24.22±1.33dA 20.21±0.77bB 17.55±0.18aC 17.20±0.15aC


Table 3.9. Mean (±SE) percentage eggs hatching on tomato plant untreated and treated with foliar application of neem across the different residue levels and dose-rates of NeemAzal®-T/S under laboratory and in greenhouse conditions.

Mean (±SE) % egg hatching (residue age, days) NeemAzal®- T/S (ml/l) 1-d 3-d 5-d 7-d


1 60.41±0.52bA 84.43±0.19bB 95.31±0.22aC 95.10±0.46aC 3 55.55±0.64cA 74.45±0.18cB 92.86±0.32bC 94.15±1.31aD 5 45.27±0.49dA 52.32±0.26dB 87.86±0.25cC 95.09±0.49aD 7 30.53±0.59eA 43.86±0.21eB 68.22±0.14dC 84.20±0.51bD

10 23.58±0.75fA 39.51±0.27fB 63.36±0.24eC 80.58±0.47cD Greenhouse Control = 0 95.40±0.45aA 95.21±0.74aA 96.89±1.44aA 95.73±0.50aA

1 57.31±0.32bA 95.50±0.41bB 94.66±0.74aB 94.73±0.56aB 3 53.69±0.29bA 82.52±0.50bB 95.12±0.67aC 95.49±0.51aC 5 43.79±0.30cA 67.31±0.49cB 94.83±1.02aC 95.56±0.53aC 7 27.02±0.75dA 47.76±0.25dB 81.04±0.55bC 95.50±0.83aD

10 22.30±0.45dA 43.18±0.84dB 71.56±0.28cC 87.87±0.39D Means followed by the same case small letters within column and upper case letters


[SAS Institute 1999]. Data were subjected to arcsine�square-root (arcsine√)

transformation before the analysis; non-transformed data on mean percentages eggs

hatching are presented in the table.

B. Laboratory

The interaction of the factors i.e. dose-rate* day was found significant for all

studied variables i.e., adult colonization (F = 34.503; df = 15, 575; P<0.0001);

egg deposition (F = 31.232; df =15,575; P<0.0001); eggs deposited/female (F =

21.957; df =15,575; P<0.0001);egg hatch (F = 220.380; df =15,575; P<0.0001)

and immatures mortality (F = 329.330; df =15,575; P<0.0001). The effect of

dose-rate significantly affected all variables compare to their respective

controls, i.e., adult colonization (F = 849.330; df = 5, 575; P<0.0001); egg

deposition (F = 682.430; df = 5, 575; P<0.0001); eggs deposited/female (F

=126.711 ; df = 5, 575; P<0.0001); egg hatch (F = 2768.251; df = 5, 575;

P<0.0001) and immatures mortality (F = 6532..024; df = 5, 575; P<0.0001).


Table 3.10. Mean (±SE) ) percentage immatures mortality of B. tabaci on tomato plant untreated and treated with foliar application of neem across the different residue levels and dose-rates of NeemAzal®-T/S under laboratory and in greenhouse conditions.

Mean (±SE) % immatures mortality (residue age, days) NeemAzal®- T/S (ml/l) 1-d 3-d 5-d 7-d


1 66.32±0.65bA 20.27±0.23bB 5.73±0.75aC 5.17±0.27aC 3 70.30±0.58cA 40.07±0.52cB 12.71±0.38bC 5.50±0.32aD 5 76.73±0.40dA 45.81±0.69dB 19.06±0.32cC 6.88±0.53aD 7 100.00±0.00eA 90.57±0.85eB 62.57±0.53dC 32.87±0.81bD

10 100.00±0.00eA 91.29±1.80eB 65.44±0.97dC 44.97±0.32cDGreenhouse Control = 0 5.47±0.42aA 5.99±0.52aA 5.29±1.12aA 5.90±0.84aA

1 64.10±0.88bA 8.12±0.40abB 5.26±1.01aC 5.70±0.72aC 3 69.80±0.90cA 11.12±0.18bB 5.33±0.92aC 5.85±1.19aC 5 75.93±1.05dA 17.14±0.31cB 5.78±0.86aC 5.16±0.55aC 7 100.00±0.00eA 50.77±1.27dB 11.88±0.48bC 5.60±0.37aD

10 100.00±0.00eA 61.06±2.14eB 18.83±0.82cC 7.81±0.44bD Means followed by the same case small letters within column and upper case letters


[SAS Institute 1999]. Data were subjected to arcsine�square-root (arcsine√)

transformation before the analysis; non-transformed data on mean percentages of

immatures mortalities are presented in the table.

Whereas the persistency of neem reduced over time i.e., adult colonization (F =

577.638; df = 3,575; P<0.0001); egg deposition (F = 541.758; df = 3,575;

P<0.0001); eggs deposited/female (F = 60.349; df = 3,575; P<0.0001); egg

hatch (4145.183; df = 3,575; P<0.0001) and immatures mortality (F = 7003.502;

df = 3,575; P<0.0001). The mean number of adult, egg deposition, eggs

deposited per female, eggs hatch and immatures mortality across the dose-

rates and day are summarized in tables 3.6, 3.7, 3.8, 3.9 and 3.10 respectively.

Foliar applied neem in the laboratory exhibited longer persistency compared to

GH conditions; for instance 6 adults WF colonized tomato plants at 10.0 ml/l on

1-d post application which increased to 20 adults (35 adults under GH

conditions) 7-d post application. Reduced colonization by WF resulted in

deposition of fewer eggs. However, an increased individual fecundity for longer

time period (5-d over 3-d post application in GH) was recorded, clearly

indicating persistency for several days. Similar to the soil application, where the


highest concentration persisted longest, the high foliar application of 10.0 ml/l

persisted longest. The dose-rate of 5.0ml/w and less become largely ineffective

in as soon as 4-d post applications and consequently there was little differences

in hatching, egg laying and immatures mortality compared to the control.

However, the mortality of immatures which was 100% for 7.0 and 10.0 ml/l on 1-

d after foliar application reduced to the extent 44% and 32% respectively on 7-d

post application.

3.4 Discussion These studies investigate the importance of the persistence of azadirachtin after

soil treatments and foliar applications for control of Bemisia tabaci in a typical

climatic region of the humid tropics. We first discuss the observed effects on a

set of chosen variables (plant choice by adults, total egg deposition, individual

fecundity, eggs hatch and mortality of immature) comparing these two

application methods. We then comment on dose relationships and the

fundamental problem of neem degradation by environmental factors by

comparison of laboratory (protected environment) and GH (close to open field)

conditions.

Persistency, adult colonization, egg deposition

Both methods of NeemAzal application, i.e. foliar application and soil drenching,

in the laboratory and in the GH resulted in reduced colonization by adults of the

treated tomato plants compared to their respective controls. The difference in

colonization preference between the two applications methods may be related

to the presence of different amounts of neem residues on the leave surface

after foliar treatment compared to soil application. With spraying, neem

compounds were deposited directly on the plant surface, the first contact region

for adults searching for feeding or egg deposition sites. After soil application

azadirachtin must be translocated from the roots to the leaves. This difference

is evident through different responses of WF in terms of adult colonization and

subsequent egg deposition behavior. Moreover, the degradation of neem was

dose dependent which has been shown by other authors who reported a

decline of efficacy with dosage (Schmutterer1985 & 1988, Barnby et al. 1989).

The deterrent effects of neem and compounds of related plant species (Melia

azedarach; Meliaceae) against Bemisia tabaci have been reported (Nardo et al.


1997, Abou-Fakhr Hammad et al. 2000 & 2001). However, when numbers of

eggs/female were calculated, it was found that, in all cases, (foliar and soil

application) either in the laboratory or in GH, freshly applied neem at high dose-

rates (7.0 and 10.0 ml/l or 2.25 or 3.0 g/l) did not reduce egg deposition; indeed

females even deposited more eggs. Thus, negative effects on egg development

can be ruled out which is in agreement with reported negative effects of

azadirachtin on reduction of ovary weight, ovary proteins and vitellogenin

synthesis (Ludlum and Sieber 1988, Rao et al. 1996), yolk synthesis, (Handler

and Postlethwait 1978); and even on the inhibition of oogenesis and ovarian

ecdysteroid synthesis (Sieber and Rembold 1983, Schulz and Schluter 1984,

Rembold 1988).

Moreover, the overall reduction in eggs deposition seems mainly related to the

anti-feedent and deterrence effect of neem. Anti-feedent actions of neem and

similar plant species resulting into decreased egg deposition behaviour of WF

have been reported in several earlier studies (Nardo et el. 1977, Coudriet et al.

1985, Abou-Fakhr Hammad et al. 2001, Hilje et al. 2003). This could be

explained by the fact that oviposition by Bemisia tabaci occurs normally while

the insect is feeding on the plant (Gammel 1974). Over time, more WF was

feeding, resulting into higher number of eggs deposited. This is consistent with

degradation of active azadirachtin on or within the leaves. The neem applied

through foliar method was deposited on the leaf surface, and was therefore

exposed to external factors, particularly light. It would therefore be expected to

degrade faster than the internally translocated azadirachtin (see also Larew

1988).

Our findings are in line with the other reported results, where feeding and

oviposition deterrence of applied neem products decreased over the time.

Showler et al. (2004) showed that neem products [Agroneem (Ajay Bio-Tech,

Pune, India), Ecozin (AmVaC, Los Angeles, CA), and Neemix 4.5 (Certis,

Columbia, MD)], was effective against Gravid Boll Weevil on cotton bolls for

only for 24-h. After 72 hrs the neem had degraded to the point that no feeding

and oviposition deterrence was observed. Moreover, this reduction in

effectiveness of applied neem was dose-rate and UV-dependent as discussed

below.


Persistency and eggs hatching

In all experiments either in the GH and the lab, hatching of WF eggs was

reduced after neem application either by topical spray or by soil drenching.

However, the percentage of hatched eggs increased over the time and

development was faster under GH compared to laboratory conditions. This

again can be related to the progressive decrease of active azadirachtin. The

hatch rate increased from about 50% up to 81% when eggs were deposited 1 or

7 day after drenching of tomato plants with 3.0 g/l NeemAzalU in the GH.

Whereas, at same dose-rate, hatch rate reached only 72% under laboratory

conditions 7-d post application, clearly indicating gradual dissipation of applied

neem. In foliar treated plants, only 23% eggs hatched on 1-d old residues, a

rate which increased to 87% 7-d post-application in GH compared to 80% under

laboratory conditions.

The reduction in eggs hatch with soil and foliar application of neem corroborates

earlier findings of Prabhaker et al. (1999) in a study with B. argentifolii and with

the GH WF (Trialeurodes vaporariorum) by von Elling et al. (2002). Observation

of the process of eclosion revealed that apparent reduction in egg hatch was

due to the effects of neem on crawlers after hatching from viable eggs, when

they come in contact with neem residues on the plant leaves and on egg

chorion and not by disruption or inhibition of embryogenesis.

Persistency and mortality of immatures The immature mortality was highest with fresh neem residue in foliar treatments

(10.0 ml/l) reaching 100%. This reduced to 7% on 7-d treatments under GH

conditions and 44% in the laboratory. Similarly, the mortality was 88% (GH) and

90% (laboratory) in soil applications, which decreased to 45% and 64% in the 7-

d treatments under GH and laboratory conditions respectively. It is obvious from

the results that degradation of applied neem was faster following foliar

application compared to soil application. Foliar treatment provided excellent

control of WF for the first few days, but rapidly degraded over time. Soil

application caused over 90% mortality but degradation was much slower and

overall effect against WF was more stable over the time The strong effect of

topical neem spray on WF immatures corroborates findings by von Elling et al.

(2002) against GHWF (Trialeurodes vaporariorum Westwood) using NeemAzal

T/S® at 0.05% and Prabhaker et al. (1999) on B. argentifolii, using Azatin E (3%


[AI] of azadirachtin; Agridyne, Salt Lake City, UT). Similarly, our result on

systemic translocation of neem agrees with the earlier reported work of

Prabhaker et al. (1999) against B. argentifolii.

Systemically induced mortality of azadirachtin has been reported in several

studies in different herbivore-plant systems. Keelberg (1992) achieved 100%

mortality in Tenthredinidae larvae by inserting a birch twig in NeemAzal

solutions (100 ppm azadirachtin). Similarly, 100% mortality in Colorado potato

beetle Leptinotarsa decemlineata Say. (Col.: Chrysomelidae) and subsequent

reduced fertility in F1 adults was reported after feeding on cut leaf stems of

potato plant places in glasses with NeemAzal solutions (100 ppm azadirachtin)

(Otto 1994). Also, systemic effect of neem against larvae of Liriomyza

huidobrensis Blanchard (Dipt. Agromyzidae) after inserting bean leaves in a

neem based insecticide (Neemix � 45, 4.5% azadirachtin; W. R. Grace & Co.,

Conn., Columbia, MD) was reported by Weintraub and Horowtiz (1997). Similar

results were obtained against western flower thrips, Frankliniella occidentalis

Thoeming et al. (2003) as well as aphids, Ossiewatsch (2000), Larew et al.

(1985).

The decrease of activity with neem-based pesticides was demonstrated in

several previous studies; a reduction in efficacy of foliar applied neem was

shown with F. occidentalis larvae, where residues of 0.1% Neemix-45 (4.5%

azadirachtin, produced by W.R. Grace & Co. - Conn., Columbia, MD, USA) on

cotton seedling were in the laboratory highly active for 10-11 days compared to

only 5 and 3-4 d in the GH and outside, respectively (Ascher et al. 2000). In a

similar study with three aphid species, Ossiewatsch (2000) recorded 100%

larval mortality after 5 d of neem application. Similarly a short residual life of

only 24 h under tropical conditions was reported by Isman et al. (1991) and that

of 6.85 days for Margosan-O, reported by (Sundaram 1996).

The progressive loss of activity of azadirachtin treatments especially under GH

conditions clearly indicated the role of abiotic factors like UV and temperature

responsible for the degradation of the active ingredient of NeemAzal. From our

results it is difficult to separate temperature and UV radiation as the driving

forces of degradation. Temperature was more or less stable under laboratory

(24-25°C) conditions, whereas in the GH a fluctuating and higher temperature

(29-39ºC) was recorded. On the other hand, the average mean UV intensity per


day recorded during the experiments under GH condition was in range of 15-16

w/m2 compared to a constant value of <1 w/m2 under laboratory conditions. We

assume that this large difference in UV radiation might have been the main

degradation factor resulting in different decrease rates of NeemAzal activity

under these two growing conditions. The rapid environment driven neem

degradation corroborates the earlier reported work of Barnaby et al. (1989),

Stokes and Redfern (1982) as well as Johnson et al. (2003). Sundram (1996)

reported fast degradation of neem if exposed to ultraviolet light or other

environmental factors. Under tropical conditions a shorter lifetime of

azadirachtin was reported by Scott and Kaushik (2000). Consequently, the rapid

UV-induced degradation of the neem products, as happened under our GH

conditions, would explain the need for frequent applications by growers in the

humid tropics.

Conclusion In summary, our study indicates that B. tabaci is highly susceptible to

NeemAzal, if application and infestation are relatively closely synchronized in

time. With more or less �fresh� azadirachtin residues in or on plants strong

effects on egg deposition, egg hatches, but particularly larval survival, are

obvious. In particular, soil drenching can lead to reliable and high efficiency.

The active ingredient dissipates over the time but with a variable rate in relation

to application method and the environmental conditions. The faster degradation

under sunlight in the GH and the longer persistency with soil treatments when

azadirachtin is protected from UV radiation within the soil or plant is best

explained by a high sensitivity of azadirachtin to the UV radiation. These

assumptions are corroborated by results of earlier reports such as those of Koul

et al. (1990), Schmutterer, (1990) and Showler et al. (2004).

The area under protected cultivation in the tropics is steadily increasing

especially in the last decade owing to higher consumer demands for safe, fresh

and clean fruits and vegetables in peri-urban areas. Tomatoes that are

cultivated under protected cultivation conditions, where they are UV exposed on

one hand and grown in pots on another giving the opportunity for a very

localized and concentrated application of neem products to the growing

substrate Thus, we foresee that substrate treatments with neem can be a

valuable tool to improve WF control on a sufficient level.

Comparative study of Azadirachtin, Avamectin & Spinosad on B. tabaci 50

Effects of Azadirachtin, Avamectin and Spinosad on Sweetpotato Whitefly Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) on

tomato plants under laboratory and greenhouse conditions in the humid tropics8 4.1 Introduction The WF, Bemisia tabaci Gennadius (Hom.: Aleyrodidae) is typically adapted to

the warm climate of tropical and subtropical regions but today enjoys a

worldwide distribution. In warmer regions (tropics, mediterranean), it is a serious

pest in open field vegetable production but crops grown under emerging

protected cultivation (film tunnels, net houses) are equally suffering under heavy

WF burden. In addition, it has recently become a significant pest of protected

horticulture in temperate regions (Butler and Heneberry 1986, Denholm et al.

1996). WF has been recorded from over 600 different plant species (Mound &

Halsey 1978, Greathead 1986, Cock 1986, Secker et al. 1998) and it feeds on a

wide variety of dicotyledonous horticultural crops like tomato, pepper, beans,

eggplant and cucumber. WF damages the crops through direct sap feeding and

producing massive quantities of honeydew. This encourages the growth of

sooty mould on leaves inhibiting photosynthesis, and causes cosmetic damage

(De Barro 1995). It is a vector of important viruses, e.g. Tomato Yellow Leaf

Curl Virus (TYLCV) (Rapisarda and Garzia 2002) and responsible for plant

disorders like uneven ripening (Maynard and Cantliffe 1989) in tomatoes. In

conclusion, the high degree of polyphagy, ingestion of phloem sap during

feeding and transmission of plant viruses between hosts, all contribute to the

serious pest status of this species (Duffus 1987, Byrne et al. 1990).

Chemical control is the primary method to manage WF, but it has two serious

drawbacks: rapid development of insecticide resistance and negative effects on

natural enemies (Gonzalez-Zamora et. al. 2004). Resistant biotypes of WF have

been described for different classes of insecticides especially

organophosphates, pyrethroids and cyclodiens, but even for the relatively new

group of chloro-nicotinyl insecticides (leading substance imidacloprid)

8 To be published as Kumar, P., and H-M. Poehling. Effects of Azadirachtin, Avamectin and Spinosad on Sweetpotato Whitefly Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) on tomato plants under laboratory and greenhouse conditions in the humid tropics. Submitted to Journal of Economic Entomology.

4


(Prabhaker et al. 1989, Dittrich et al. 1990a, Cahill et al. 1995, Byrne et. al.

2003). To avoid selection of resistant biotypes a careful management with

frequent changes of active ingredients is desirable. Furthermore, conventional

insecticides bear a high risk for farmers and consumers because of toxicity and

residues on the produces after harvest, particularly if decreasing efficacy

(resistance) is counteracted by increased dosage or application frequency. The

philosophy of integrated plant management recommends effective pesticides

that have low mammalian toxicity, low persistence in the environment and high

degree of selectivity. To minimize the above problems this study investigates

biopesticides or botanicals of natural origin under the special conditions of the

humid tropics.

Azadirachtin (product: NeemAzal®TS), a steroid-like tetranortriterpenoid derived

from Neem trees (Azadirachta indica Juss.), is a strong anti-feedent, repellent

and growth regulating compound for a wide variety of phytophagous insects,

including WF (Schmutterer 1990, Coudriet et al. 1985). It delays or prevents

moulting, reduces growth, development and oviposition; and can cause

significant mortality particularly in immatures (Coudriet et al. 1985, Flint and

Sparks 1989, Prabhaker et al. 1989, Schmutterer 1990, Liu and Stansly 1995,

Mitchell et al. 2004). Neem preparations are commercially available worldwide,

but especially in most countries in the humid tropics. However, the efficacy

seems to be highly variable (Puri et al. 1994, Leskovar and Boales 1996, Akey

and Henneberry 1999). This is partly caused by variable contents of the active

ingredient of different products. The NeemAzal used in this study is of a very

reliable and consistent quality. A major drawback of neem active ingredients is

their sensitivity to UV-radiation and temperature and fast degradation under

open field conditions (Stokes and Redfern 1982, Barnaby et al. 1989, Johnson

et al. 2003, Barrek et al. 2004).

Spinosad consisting of 85 % Spinosyn A and 15% Spinosyn D (product:

Success®) is a bio-rational pesticide derived from aerobic fermentation of the

soil microorganism Saccharopolyspora spinosa with a world wide use on over

200 crops against insect-pest of several orders including Lepidoptera, Diptera,

Thysanoptera, Siphonaptera, Coleoptera and Hymenoptera. It is classified as a

reduced-risk pesticide by the US Environment Protection Agency (Cleveland et

al. 2001). It is reported to be relatively less active against mites and sucking


insect-pests (Boek et al. 1994, Dow 1997, Bret et al. 1997, Thompson et al.

2000). Spinosad acts through ingestion and contact and kills the insects through

targeting the nervous system (Salgado 1997 and 1998, Thompson et al. 2000,

Cowles et al. 2000, Tjosvold and Chaney 2001). Concerning its selectivity no

general rule can be given. It is of low toxicity for mammals but for non-target

insects a broader spectrum of activity is reported. Fresh residues are described

to affect pollinators like honey or bumblebees (Miles et al. 2002, Mayes et al.

2003, Morandin et al. 2005). It is moderately toxic to commonly used biological

control agents like Amblyseius cucumeris Oudeman (Acarina; Phytoseiidae)

and Orius insidiosus Say (Hemiptera:Anthocoridae) (Pietrantonio and Benedict

1999, Ludwig and Oetting 2001). However, it is highly toxic to the commonly

used whitefly parasitoid, Encarsia formosa (Hym: Aphelenidae) even after 28-

day post application (Jones et al. 2005). It is also toxic to the egg parasitoid

Anaphes iole (Hymenoptera: Mymaridae) (Williams et al. 2003). The

persistency of spinosad is limited to a few days in presence of direct sunlight

(Saunders and Brett 1997), thus devoid of any long term effects for natural

enemies.

Abamectin (product: Avermectin) is derived from a soil microorganism

Streptomyces avermitilis. It consists of 80% avermectin B1a and 20%

avermectin B1b as active ingredients. It acts by affecting the nervous system of

insects and is highly toxic to a broad spectrum of insects, if they are

contaminated by fresh spraying solutions or residues. Mammals can be affected

only by ingesting high dosages (Ray 1991). Similar to spinosad, it is toxic to

honey bees and other pollinators and to water organisms. It could be rapidly

degraded, when present as a thin film on treated leaf surfaces. In the presence

of light, its half-life as a thin film was measured as 4- 6 h regardless of surface

or foliage type (Wislocki et al.1998). However, other studies reported much

longer persistence (Reis et al. 2004). Abamectin does not persist or accumulate

in the environment. Its instability, as well as its low water solubility and tight

binding to soil, limits its bioavailability for non-target organisms and prevents it

from leaching into groundwater or entering the aquatic environment (Lasota &

Dybas 1990).

Apart from our earlier studies on impact of Azadirachtin on Bemisia tabaci

(Kumar et al. 2005) little is known about the efficacy of these natural pesticides


against WF in Thailand and elsewhere in the SE Asia. Efficacy of abamectin

against WGWF, T. Vaporariorum, was reported by Wang et al. (2003) and a

similar effect of spinosad in northwestern Europe against this species and

against Bemisia tabaci in Israel was described by Schoonejans and Van der

Staaij (2001) and Ishaaya et al. (2001) respectively.

We assume that these botanical pesticides could improve the management of

B. tabaci particularly in terms of safety for growers and consumers in the humid

tropics in general and in protected cultivation systems in particular. Hence, we

conducted a series of experiments under controlled (air conditioned laboratory)

conditions and in tropical net greenhouses to evaluate the direct contact toxicity

and residual persistence of these botanicals at different concentrations on the

colonization preference of WF adults, oviposition pattern, egg hatch and

immature mortality.

4.2. Materials and Methods Location, host plant and rearing of whiteflies

The study was part of an interdisciplinary research project funded by the



Experiments were conducted with tomato plants (Lycopersicon esculentum Mill

(Solanaceae), cv. King Kong II) at the greenhouse and laboratory complex at

the Asian Institute of Technology, Bangkok, Thailand. The initial WF culture was

obtained from the DoA (Department of Agriculture) Virology section, Chatuchak,

Bangkok, which was maintained there without any pesticide exposure for two

years. For the experiments mass rearing was established on tomatoes grown in

air conditioned rooms. WF was kept in insect-proof cages (1.20 x 65 x 65 cm) at

24± 2°C and 60-70% relative humidity (rH). WF stages of same age, i.e. L1, L2

and adults, were obtained by allowing female B. tabaci to lay eggs for 24 h on

caged tomato plants. Thereafter, adults were removed from the cages using an

aspirator. Plants with eggs were further cultivated for synchronized

development of B. tabaci. Plants with L1, L2, L3 or pupae were used for the

experiments (see below) or kept until adult emergence in order to obtain adults

of similar age. The laboratory and greenhouse experiments presented below

were carried out from September 2004 until February 2005.


Pesticides

Pesticides used were: NeemAzal®-TS (1% Azadirachtin A = AZA) (Trifolio M

GmbH, Lahnau, Germany), Success® (Spinosad 12% (wt: vol) Sc, Dow

Agrosciences, Indianapolis, IN], and Abamectin [1.8% Avermectin (wt: vol.) EC,

produced by: Exphoreflex Industrial, Thailand; Imported by: Inter Crop Co. Ltd.,

Thailand]. No recommend dose-rates for abamectin and spinosad against WF

were available in Thailand. Dose rates chosen were 2-6ml/l and were based on

recommended dose-rates of 1-4 ml of both commercial products/liter water for

Plutella xylostella, Helicoverpa armigera (Hubner) and Spodoptera spp. on

Brassicaceous crops and experience from preliminary experiments with WF.

Neem was applied at the recommend dose-rate of 5 ml (0.05 g AZA)

NeemAzal® TS/l and, to study dose-relation further, with 10 (0.1 g AZA) and 15

(0.15 g AZA) ml/l. All three products were diluted to spraying solutions with tap

water which was also used for the untreated control. Approximately 50 ml of the

product solutions were applied per plant using a small (500 ml capacity) hand

held sprayer. Treatments

All experiments were conducted on tomato plants cv. King Kong II grown in 10

cm diameter plastic pots with 180 gram of local substrate (pH-5.3; organic

matter - 28%; sand - 30%; silt - 39%; clay - 31%; total N - 0.4%; K - 0.65%; P -

0.18%; Ca - 0.08%). Plants were kept in an air-conditioned laboratory at 24±

2°C, 60-70% rH and a photoperiod of 16:8 h (Light: Dark).

Experiment 1: Direct Toxicity

The direct toxicity of NeemAzalTS (5, 10 and 15 ml/l), abamectin (2, 4 and 6

ml/l) and spinosad (2, 4 and 6 ml/l) was tested against eggs, larvae (L1, L2 &

L3), and pupal stage of B. tabaci. All experiments were carried out with 6

replications of each treatment and the experiments were repeated thrice over

time.

To measure ovicidal effects three different age group, i.e. 1, 3 and 5-d old eggs

were selected from synchronized eggs batches with 50 eggs of each group/per

plant (rest removed by means of an entomological pin under microscope).

Afterwards, plants were treated with the compounds at the stated dose rates.

Treated plants were stored until emergence of the L1 and, thereafter, the

proportion of hatched individuals calculated.


Similarly, 50 synchronized immature stages per plant were marked for easy

individual counting and identification. Afterwards, batches of plants were treated

7 (L1), 10 (L2) and 14 (L3) days after egg laying. Dead larvae/pupae on the

leaflets were counted daily. Immatures (larvae/pupae) were considered dead

when they lost their normal yellow-green color, turgidity and smooth cuticle

structure.

The effects of all three products on B. tabaci pupae were checked again with

three different age groups, i.e. 1, 3 and 5-d old pupae. Emerging adults were

counted daily and the proportion of dead individuals calculated by comparison

with the non-hatched numbers of pupa.

Experiment 2. Residual toxicity

General procedure and plant treatments

Potted 15-day old tomato plants were sprayed with 5 and 10 ml/l NeemAzalTS

and 4 and 6 ml/l abamectin and spinosad on the adaxial and abaxial leaf

surfaces until run-off at 15, 10, 5 and 1- day prior to introducing WF. Plants

sprayed with tap-water served as controls. Plants were arranged in a

randomized design in a transparent acrylic box (1.2 m height, 75 cm width) and

at day 0 approximately 400 same-aged un-sexed adult WF (2-d old) were

released into the cages for 72 h. to give adult WF sufficient time for plant choice

and oviposition.

Laboratory conditions Plants were cultivated in an air conditioned laboratory. Starting one -day after

the release, all adult WF per plant were counted for three consecutive days to

record the colonizing preference of WF. Thereafter, WF adults were removed

from the boxes and WF eggs on each leaflet counted using a microscope.

Plants were further maintained in WF-free cages to allow juveniles to develop.

After 30 days, plants were removed from the boxes and the number of living

and dead immatures and empty pupal cases were counted to record adult

emergence and immature mortality.

Greenhouse conditions After treatment, plants were arranged in acrylic boxes for exposure to WF as

mentioned above. Boxes were established in a net greenhouse (6x3x3 meter:

net 78 mesh, Econet®; Ludvig Swensoon, Sweden) and exposed to WF. Adults

were counted for three days. Afterwards, plants carrying WF eggs were


removed from the boxes, eggs counted, marked and plants arranged inside a

similar WF-free net house to allow juveniles to develop under greenhouse

condition. Data for egg hatch and immature mortality were calculated as in the

above-mentioned experiments. Both experiments were carried out with 6-

replication for each treatment and 2 repetitions over time.

Statistical Analyses Data for percentage egg hatch, immature mortality and adult emergence were

subjected to HOVTEST = LEVENE option of SAS to account for homogeneity of

variance and normality. In the case of non-homogeneity, percent values were

transformed using arcsine�square-root (arcsine√) transformation. Insect count

values were transformed by square-root (√) transformation before running an

ANOVA (Steel and Torrie 1980, Gomez and Gomez 1984). The data was

analyzed using the PROC GLM procedure in SAS to determine single or

interaction effects of factors (SAS 1999). Whenever significant interaction was

observed between factors, the level of one factor was compared to each level of

the other factor by all pair wise multiple comparison procedures (Tukey�s test)

unless mentioned otherwise. All data are presented as mean± SE. A significant

level of ∝ = 0.05 was used for all analyses.

4.3. Results Experiment1: Direct Toxicity

Egg hatch was significantly affected by the interaction of the age of treated eggs

(age class) and the concentration of NeemAzalTS (concentrations*age class:

F=44.05; df =6,143; P< 0.0001). Hence percentage of the larval emergence of

each age class was compared at each concentration level of NeemAzalTS (see

table 4.1).


Table 4.1. Mean (±SE) % of B. tabaci larvae hatching from eggs treated at different ages on tomato plants by foliar spraying with different concentrations of NeemAzalTS.

Means followed by the same lower case letters within column and uppercase letters

within the rows are not significantly different (P: 0.05; Tukey�s multiple comparison test;

SAS Institute 1999). Data on % egg hatching was subjected to (arcsine√)

transformation before analysis; non transformed percentages of eggs hatching are


Hatch success was least from eggs treated on day-5 with all concentrations

compared to 3-day and 1-day old WF eggs. In contrast, no significant

interaction was found in larval emergence between the egg age-class and

concentrations of either spinosad (F= 0.55; df =6,143; P = 0.767) or abamectin

(F = 0.26; df = 6,143; P = 0.953). Thus, concentrations were compared

irrespective of the levels of the age classes and vice versa (see table 4.2).

spinosad significantly reduced larval emergence in relation to the water control

(F = 3061.97; df = 3,143; P < 0.0001) in a dose dependent manner (see table

4.2). Abamectin treatment, however, completely inhibited larval development

within the eggs.

In all NeemAzalTS treatments, cumulative larval mortalities increased rapidly

with time reaching, in all larval stages, 100% mortality latest after 4 days with

concentrations of 10 and 15 ml/l. Only with the lowest dosage of 5 ml/l a

reduced initial efficacy could be observed (Fig. 4.1 A-C).

Egg age-classes (d) treated Concentration NeemAzalTS

1-d 3-d 5-d 0 ml/l (control) 99.33±0.28aA 98.33±0.17aA 98.59± 0.17aA

5 ml/l 54.00±1.74bA 45.33±0.99bB 21.17±0.76bC 10 ml/l 7.33±0.62cA 2.33±0.33cB 0.00±0.00cC 15 ml/l 2.17±0.63dA 0.00±0.00dB 0.00±0.00dB


Table 4.2. Mean (±SE) % of B. tabaci larvae hatching from eggs treated at different ages on tomato plants by foliar spraying with three concentrations of Abamectin and Spinosad

Concentration of pesticides Bio-pesticides 0 ml/l 2 ml/l 4 ml/l 6 ml/l Abamectin 99.78±0.11a 0±0b 0±0b 0±0b Spinosad 99.61± 0.13a 68.00± 0.60b 43.50± 0.73c 22.22±0.78d

Values in rows followed by same letters are not significantly different (Tukey�s HSD

test; P<0.05)

The cumulative mortalities of treatments compared to the control were

significantly different at all three stages, L1 (F = 2671.04; df=3, 71; P <0.0001),

L2 (F = 5950.98; 3, 71; P < 0.0001), L3 (F =4845.60; 3, 71; P <0.0001) but

within treatments above all the lowest concentration of 5 ml/l separated clearly

from the 10 and 15ml/l dose-rates. Similarly, with spinosad, all concentrations

resulted in 100% mortalities in all three larval stages latest at day 8 after

treatment with no significant differences among concentrations (see fig 4.2 A-

C). The final accumulated mortalities differed significantly from the control at all

three larval stages, L1 (F = 5997.45; df =3, 71; P <0.0001), L2 (F = 9317.38;

df=3, 71; P <0.0001), L3 (F = 17573.4; df=3, 71; P < 0.0001). In contrast,

abamectin caused 100% mortalities in all concentrations and all three larval

stages within 24 hrs of treatment, which was highly significant compared to the

control. Hence daily cumulative mortalities were not calculated L1 (F = 5120.59;

df=3, 71; P <0.0001), L2 (F = 38302.8; df=3, 71; P <0.0001, L3 (F = 9317.38;

df=3, 71; P <0.0001).


Fig.4.1. Mean (±SE) percentage of cumulative mortality in the first larval stage (A), second stage larvae (B) and third stage larvae (C) of the B.

tabaci to the three concentrations (5, 10 and 15 ml/l) of NeemAzalTS during 10 consecutive days. Values sharing a common letter(s) (within individual days after exposure) are not significantly different at P < 0.05, Tukey’s HSD test).

D a y s a f t e r e x p o s u r e

1 -d 2 - d 3 -d 4 -d 5 - d 6 -d 7 -d 8 -d 9 -d 1 0 -d0

2 0

4 0

6 0

8 0

1 0 0

abcd

a a a a a a a a a

bb

b

b

bb b b b

c

c

c cc

c ccc

cc c

c cc

dd

dd

(C )

( B )

Mea

n (±

SE) %

cum

ulat

ive

mor

talit

y

0

2 0

4 0

6 0

8 0

1 0 0

W a t e r N e e m ( 5 m l / l ) N e e m ( 1 0 m l / l ) N e e m ( 6 m l / lw )

d

cb

a a a aaaaaaa

b

b

bb b b b b b

c

cc ccc c c c

cccccccd

d

0

2 0

4 0

6 0

8 0

1 0 0

a

b

c

d

a a a a a a a a a

b

b

bb

c

cd

d cc c

b

bc

cc

cc

bcc

bcc

(A )

bcc


Fig.4.2. Mean (±SE) percentage of cumulative mortality in the first larval stage (A), second stage larvae (B) and third stage larvae (C) of the B.

tabaci to the three concentrations (2, 4 and 6 ml/l) of Spinosad during 10 consecutive days. Values sharing a common letter(s) (within individual days after exposure) are not significantly different at P < 0.05, Tukey’s HSD test).

D a y s a f te r e x p o s u r e1 -d 2 -d 3 - d 4 -d 5 -d 6 -d 7 -d 8 -d 9 -d 1 0 -d

0

2 0

4 0

6 0

8 0

1 0 0

aa

a

a a a a a a

bc

d

bb

bb

c

b

b

b

d

c c

d

c

dd

c

d

c

c

(C )cc

bbb

bbb

a

a0

2 0

4 0

6 0

8 0

1 0 0

aa a a a a a a a

bc

d

b

b

b

b

b b bbb

bbb

bb

bbb

c

c

c

c

d

d

d

dcc

( A )

Mea

n (±

SE) %

cum

ulat

ive

larv

al m

orta

lity

0

2 0

4 0

6 0

8 0

1 0 0

W a te r S p in o s a d ( 2 m l/ lw ) S p in o s a d ( 4 m l/ lw ) S p in o s a d ( 6 m l/ lw )

a

a

a a a a a a a

bc

db

b

b

b

c

b

bbc

c

c

c

c

dcc cc

c( B )

cc

bbb

bbb

a


Pupal mortality expressed by the proportion of empty pupal cases was affected

significantly by the interaction of the pupal age when treated and NeemAzalTS

concentrations (concentrations*age class); concentrations (F=7330.79; df

=3,143; P< 0.0001); pupal age-class (F=6.60; df =2,143; P = 0.001).

Hence, the mortality of each age class was compared at each level of the tested

NeemAzalTS concentrations (see table 4.3). Mortality did not differ for 1 and 3-d

old pupa but increased significantly if pupae were already 5-d old at treatment

with NeemAzalTS concentrations of 5 and 10 ml/l. In contrast, no significant

interaction was found in pupal mortality between the pupal age-class and the

tested concentrations of spinosad (F= 1.64; df=6,143; P = 0.141). Significant

differences were observed for concentrations (F= 36242.6; df=3,143; P<

0.0001), but not for pupal age-class (F= 1.63; df=2,143; P = 0.1993). Similarly,

no interaction in tested concentrations and age-class occurred for abamectin (F

= 1.64; df = 6,143; P = 0.144). Thus, concentrations of spinosad and abamectin

were compared irrespective of the levels of the age classes and vice versa.

Table 4.3. % mortality (±SE) of B. tabaci pupae treated at different ages on tomato plants by foliar spraying with different concentrations of NeemAzalTS under laboratory conditions.

Means followed by the same lower case letters within column and upper case letters

within the rows are not significantly different (P: 0.05; Tukey�s multiple comparison

test; SAS Institute 1999). Data on % pupal mortality was subjected to (arcsine√)

transformation before analysis; non transformed percentages of eggs hatching are


Pupal age-class Concentration NeemAzalTS 1-d old 3-d old 5-d old 0 ml/l(control) 0.33±0.22aA* 0.17±0.17aA 0.33±0.22aA

5 ml/l 57.50±2.19bA 58.00±2.26bA 61.33±0.67bB 10 ml/l 79.83±0.76cA 80.00±0.74cA 85.50±1.02cB 15 ml/l 100±0dA 100.±0dA 100.00±0.00dA


Experiment 2. Residual Toxicity

Laboratory conditions

Interaction of concentrations of all three biopesticides * days were significant for

all variables (plant choice, egg deposition and hatch and mortality) studied:

plant choice (F=25.70; df = 18, 335; P<0.0001); egg deposition (F = 39.42; df =

18,335; P<0.0001); egg hatch (F = 89.93; df = 18,335; P<0.0001) and immature

mortality (F = 1428.07; df = 18,335; P<0.0001). The mean number of adult WF

colonizing the plants, numbers of deposited eggs, percentage eggs hatched

and mortality rates of immatures across the concentrations and days are

summarized in the tables 4.4, 4.5, 4.6, & 4.7 respectively. The results showed

that activity of abamectin residues persisted longest compared to spinosad and

NeemAzalTS. Neem degraded faster than spinosad in all laboratory tests and

its degradation was clearly concentration-dependent. In contrast, degradation of

abamectin was less related to the applied concentrations; and spinosad was

much less so.

Table 4.4. Mean (±SE) numbers of adult whiteflies settling on tomato plants with different aged foliar residues of NeemAzalTS, Spinosad and Abamectin under laboratory conditions.

Residue age, days Treatments 1-d 5-d 10-d 15-d Water 27.92±1.28aA 29.92±1.28aA 32.92±1.58aA 28.50±1.93aA

Neem (5ml/l) 11.93±0.39bA 26.75±1.18aB 30.50±1.46aB 29.17±1.60aB Neem (10 ml/l) 7.13±0.37cA 15.75±0.73bB 30.00±1.42aC 31.25±1.42aC

Abamectin (2 ml/l) 5.67±0.36cA 1.67±0.36cA 01.58±0.29bA 2.08±0.08bB Abamectin (4 ml/l) 0.50±0.19dA 0.42±0.15dB 0.67±0.14bBC 1.25±0.13bC Spinosad (2 ml/l) 29.17±1.39aA 28.08±1.21aA 28.83±1.58aA 29.08±1.48aA Spinosad (4 ml/) 26.08±1.48aA 29.67±1.77aA 30.00±1.44aA 28.33±1.16aA



SAS Institute 1999). Data on number of adult WF was subjected to square-root

transformation before analysis; non transformed numbers of adult WF are presented in

the table.


Table 4.5. Mean (±SE) numbers of egg deposition on tomato plants untreated and treated with foliar application of NeemAzalTS, Spinosad and Abamectin across the different residue levels and concentrations under laboratory conditions.

Residue level Bio pesticides Concentrations 1-d old 5-d old 10-d old 15-d old

Water 321.92±9.19aA 324.00±13.25aA 325.42±11.82aA 323.75±13.60aANeem (5ml/l) 116.25±4.16bA 265.92±6.68bB 327.00±6.51aC 321.33±14.50aC

Neem (10ml/l) 65.75±3.72cA 185.75±7.78cB 270.50±13.09bC 323.17±13.78aDAbamectin (2ml/l) 25.08±1.34dA 27.17±1.48dA 26.33±1.40cA 22.58±1.02bA Abamectin (4ml/l) 12.92±1.05eA 15.67±0.87dA 15.00±0.83dA 14.17±0.88bA Spinosad (2ml/l) 307.83±9.35aA 309.67±9.13abA 312.17±11.67abA 324.42±19.87aASpinosad (4ml/) 302.75±7.38aA 284.50±12.40aA 319.50±13.19abA 323.33±19.50aA



SAS Institute 1999). Data on number of eggs deposition was subjected to square-root

transformation before analysis; non transformed number eggs depositions by adult WF

are presented in the table.

Table 4. 6. Mean (±SE) percentage of eggs hatching on tomato plants untreated and treated with foliar application of NeemAzalTS, Spinosad and Abamectin across the different residue levels and concentrations under laboratory conditions.



SAS Institute 1999). Data on percentage eggs hatch was subjected to arcsine square-

root transformation before analysis; non transformed percentage eggs hatch data are


Residue level Bio pesticides & Concentrations 1-d old 5-d old 10-d old 15-d old

Water 97.75± 0.52aA 96.61±0.60aA 99.60±0.76aA 98.98±0.22aANeem (5ml/l) 45.37± 1.82bA 88.18±0.51bB 91.96±0.55bC 98.58±0.35aDNeem (10ml/l) 24.32±0.60cA 65.36±0.93cB 85.61±0.77cC 97.30±0.44aD

Abamectin (2ml/l) 19.23±1.48cA 18.95±1.70dA 17.67±0.86dA 20.48±0.79bAAbamectin (4ml/l) 6.34±0.97dA 7.01±0.87eB 7.55±1.29eC 9.20±1.05cC Spinosad (2ml/l) 68.38±0.41eA 67.98±0.97cA 69.90±0.79fA 77.99±0.37dBSpinosad (4ml/) 44.74±0.87bA 44.89±0.96fA 48.94±0.12gA 56.23±0.43eB


Table 4.7. Mean (±SE) percentage of immatures mortality on tomato plants untreated and treated with foliar application of NeemAzalTS, Spinosad and Abamectin across the different residue levels and concentrations under laboratory conditions.


Water 2.76±0.24aA 3.22±0.26aA 3.11±0.14aA 2.84±0.25aA Neem (5ml/l 76.31±0.76bA 20.73±1.25bB 3.91±0.26aC 3.37±0.43aC

Neem (10ml/l) 100.00±0.00cA 65.11±1.16cB 25.16±0.13bC 7.71±0.43bD Abamectin (2ml/l) 100.00±0.00cA 100.00±0.00dA 100.00±0.00cA 100.00±0.00cAAbamectin (4ml/l) 100.00±0.00cA 100.00±0.00dA 100.00±0.00cA 100.00±0.00cASpinosad (2ml/l) 95.77±0.17dA 94.16±0.32eA 93.22±0.48dB 91.80±0.28dC Spinosad (4ml/) 100.00±0.00cA 100.00±0.00dA 100.00±0.00eA 100.00±0.00eA



SAS Institute 1999). Data on percentage immatures mortality was subjected to arcsine

square-root transformation before analysis; non transformed percentage immatures

mortality data are presented in the table.

Greenhouse conditions

Similar to the laboratory, in greenhouse, residue bioassay for the interaction of

concentration of all three pesticides*day were significant for all studied

variables, plant choice (F = 28.81; df = 18, 335; P<0.0001); egg deposition (F =

31.47; df = 18,335; P<0.0001); egg hatch (F = 135.40; df = 18,335; P<0.0001)

and immature mortality (F = 646.80; df = 18,335; P<0.0001). Comparable to the

laboratory tests, the relevant data are listed in the tables 4.8, 4.9, 4.10, and

4.11. Like in the laboratory conditions, NeemAzalTS lost its activity faster than

spinosad and abamectin as expressed through colonization, egg deposition,

egg hatch and immature mortality of WF. Mortality for immatures decreased to

control level even after 5 days and therefore much faster then in the laboratory.

Abamectin showed longest persistency in the greenhouse, where its residue

remained active for15-days post-application. Apparently, abamectin has low

effect on hatch of eggs but it functioned as a strong oviposition deterrent and

caused 100% mortality at all residue levels tested. spinosad residues remained

effective for long time, particularly concerning immature mortality. But it neither


deters the WF to settle onto the tomato plants nor was it a strong oviposition

deterrent, and had only a moderate effect on egg hatch. Table 4.8. Mean (±SE) numbers of adult whiteflies, on tomato plants untreated and treated with foliar application of NeemAzalTS, Spinosad and Abamectin across the different residue levels and concentrations under greenhouse conditions.


Water 29.68±1.28aA 31.08±1.52aA 28.83±1.35aA 30.92±1.45aANeem (5ml/l) 8.33±0.53bA 26.67±0.92aAB 29.50±1.50aB 31.33±1.73aB

Neem (10ml/l) 6.30±0.52bA 15.75±0.64bB 29.75±1.59aC 30.00±1.42aCAbamectin (2ml/l) 2.00±0.28cA 1.67±0.36cA 1.92±0.29bA 2.25±0.13bA Abamectin (4ml/l) 1.08±0.08cA 0.42±0.15cB 1.08±0.08bC 1.42±0.15bC Spinosad (2ml/l) 28.62±1.20aA 31.92±1.56aA 30.00±1.48aA 31.25±1.30aASpinosad (4ml/) 29.92±1.30aA 30.42±1.60aA 30.08±1.33aA 29.33±1.39aA



SAS Institute 1999). Data on number of adult WF was subjected to square-root

transformation before analysis; non transformed numbers of adult WF are presented in

the table.

Table 4.9. Mean (±SE) numbers of egg deposition on tomato plants untreated and treated with foliar application of NeemAzalTS, Spinosad and Abamectin across the different residue levels and concentrations under greenhouse conditions.


Water 324.83±2.44aA 330.58±11.51aA 314.92±13.91aA 321.00±17.00aANeem (5ml/l) 114.42±9.47bA 283.00±11.96aB 311.00±8.57aB 318.67±15.90aB

Neem (10ml/l) 59.83±3.78cA 202.92±12.98bB 300.42±15.55aC 320.25±12.98aCAbamectin (2ml/l) 24.33±1.37dA 24.75±1.42cA 32.33±2.57bA 34.08±2.70bA Abamectin (4ml/l) 12.83±1.01eA 14.08±0.83cAB 18.33±1.74bBC 27.50±2.32bC Spinosad (2ml/l) 311.83±11.89aA 309.17±16.94aA 316.67±9.89aA 316.50±14.42aASpinosad (4ml/) 314.00±17.07aA 311.67±11.28aA 318.67±13.13aA 317.83±13.74aA



SAS Institute 1999). Data on number of eggs deposition was subjected to square-root

transformation before analysis; non transformed number eggs depositions by adult WF

are presented in the table.


Table 4.10. Mean (±SE) percentage of eggs hatching on tomato plants untreated and treated with foliar application of NeemAzalTS, Spinosad and Abamectin across the different residue levels and concentrations under greenhouse conditions.


Water 99.61±0.46aA 98.63±0.48aA 97.85±0.62aA 99.73±0.29aANeem (5ml/l) 45.12±0.87bA 91.89±1.11bB 97.15±0.36aC 97.67±0.37aC

Neem (10ml/l) 23.79±1.29cA 72.19±0.91cB 97.67±0.21aC 97.46±0.59aCAbamectin (2ml/l) 18.90±1.12cA 17.55±1.04dA 17.81±1.76bA 20.51±1.56bAAbamectin (4ml/l) 8.32±0.65dA 7.35±0.40eA 7.75±0.98cA 8.94±1.69cA Spinosad (2ml/l) 67.34±0.93eA 69.62±0.49cA 74.95±0.27dB 81.78±0.81dCSpinosad (4ml/) 45.78±0.45bA 46.87±0.35fA 49.76±0.72eBC 54.60±1.50eC



SAS Institute 1999). Data on percentage eggs hatch was subjected to arcsine square-

root transformation before analysis; non transformed percentage eggs hatch data are


Table 4.11. Mean (±SE) percentage of immatures mortality on tomato plants untreated and treated with foliar application of NeemAzalTS, Spinosad and Abamectin across the different residue levels and concentrations under greenhouse conditions.


Water 2.36±0.18aA 1.90±0.17aA 2.19±0.16aA 2.87±1.75aA Neem (5ml/l) 74.39±0.96bA 3.05±0.19aB 2.86±0.13aB 3.64±0.32aB

Neem (10ml/l) 100.00±0.00cA 19.64±0.31bB 12.03±1.11bC 4.26±0.29aD Abamectin (2ml/l) 100.00±0.00cA 100.00±0.00cA 100.00±0.00cA 100.00±0.00bAAbamectin (4ml/l) 100.00±0.00cA 100.00±0.00cA 100.00±0.00cA 100.00±0.00bASpinosad (2ml/l) 97.64±0.24dA 96.78±0.38dB 89.65±0.57dC 87.23±0.64cD Spinosad (4ml/) 100.00±0.00cA 100.00±0.00cA 97.10±0.46eB 89.31±1.46dC



SAS Institute 1999). Data on percentage immatures mortality was subjected to arcsine

square-root transformation before analysis; non transformed percentage immatures

mortality data are presented in the table.


4.4. Discussion Direct Contact Toxicity The results show that the sensitivity of B. tabaci eggs for azadirachtin changes

with progressing development. This corroborates earlier findings of Prabhaker

et al. (1999) with a similar species, B. argentifolii. However, no such age

specific effects were observed in the case of abamectin and spinosad-treated

eggs. These are in contrast to an earlier study of Wang et al. (2003) with T.

vaporariorum treated with abamectin. The different results may be explained by

the different concentrations of abamectin used. Our concentrations selected

were in the saturation part of the dose-response curve. Inductions of embryonic

disruptions by abamectin are reported from other abamectin-herbivore systems

like Liriomyza huidobrensis (Schuster and Everett 1983, Ochoa and Carballo

1993, Buxton and McDonald 1994). In contrast, the missing concentration

response of spinosad is in line with earlier reports on GHWF (T. vaporariorum),

where no effect of concentration was found on various egg stages and where

an overall efficacy of over 98% was reported for all tested age-classes

(Schoonejans and Van der Staaij 2001). Examination of the process of

embryonic development revealed that abamectin-treated eggs changed color

from dark brown to black presumably indicating the death of developing

embryo. In neem and spinosad-treated eggs, no such color change took place

and apparently more the influence on a successful egg hatch was the key

mechanism resulting in killing the emerging crawlers immediately after eclosion

from viable eggs, when they came into contact with neem and spinosad

residues on the plant leaves and on the egg chorion (Schoonejans and Van der

Staaij 2001 & Ishaaya et al. 2001). Byrne et al. (1990) demonstrated that WF

eggs are closely connected to the leaf tissue, e.g. extracted water from plant

tissue accounts for 50% of the egg mass. Consequently, also translaminar

translocated ingredients can be expected to penetrate in small quantities via

plant into the embedded eggs. With its high toxicity even small amounts of

abamectin might have caused such deleterious effects and the penetration into

the maturing egg may be more intensive then with younger stages (see Wang

et al. 2003).

Moreover, abamectin was very toxic for the larval stages, since all died within

24 hours after treatment. In contrast, mortality induced by neem and spinosad


decreased gradually with aging of larvae; the first larval stage was found more

susceptible than the other two older stages for both ingredients. In the case of

neem, this findings agree with earlier studies of Coudriet et al. (1985), Lindquist

and Casey (1990), Price and Schuster (1991) and the results corroborate with

findings of Schoonejans and Van der Staaij (2001), who tested spinosad

against T. vaporariorum. Comparing abamectin and spinosad, a striking

difference was found in the speed of action: high mortality rates in abamectin

were reached within 24 hrs whereas with spinosad it takes 6-9 d before the final

mortality values were reached. The lower daily mortality from spinosad could be

due to its slow penetration rates and slow metabolism once inside the insect

body (Sparks et al. 1998, Sparks et al. 2001), which results in such a delayed

but steady increasing activity.

Similar to the egg stage the intensity of reaction of B. tabaci pupae to

NeemAzalTS depends on the pupal age at treatment. The least number of adult

WF emerged from the 5-d old neem-treated pupae compared to 1 and 3-d old.

Similar to its effect on egg stage it could be due to the presence of residues,

killing the emerging WF coming out of the puparia. Our results corroborate

earlier work with T. vaporarium where a concentration of 0.5% NeemAzal T/S

significantly reduced the proportion of emerging adults (von Elling et. al. 2002).

In contrast, all tested concentration of spinosad and abamectin killed the adults

within the pupal stage by 100%. Similar results are reported with abamectin

against pupae of T. vaporarium by Wang et al. 2003. However, our results do

not agree with findings of Schoonejans and Van der Staaij (2001), who did not

find any effect of spinosad on pupae of T. vaporariorum.

Residual toxicity

Abamectin most efficiently deterred both in laboratory and in greenhouse, the

settling of WF adults on the tomato plants; followed by weaker but pronounced

effects of neem. In contrast, spinosad showed no inhibition of adult colonization

either as fresh or 15-d old residues. The dissimilar colonization behavior of adult

WF resulted in unequal egg deposition. Anti-feedent actions of neem resulting

in decreased egg deposition behavior of WF are reported in several studies

(Nardo et el. 1977, Coudriet et al. 1985, Abou-Fakhr Hammad et al. 2001, Hilje

et al. 2003). The intensity of oviposition by B. tabaci is normally in relation to its

feeding activity (Gammel 1974) and deterrent effects often reduce not only


settling but also phagostimulation. Oviposition suppressant effects of neem

products have also been documented for different other insect orders i.e.

Orthoptera, Heteroptera, Homoptera, Hymenoptera, Lepidoptera, and Diptera

(Saxena, 1989, Singh 1993, Schmutterer 1995, Isman 1996). The results with

abamectin are consistent with studies of Horowitz et al. (1997), where

abamectin considerably reduced oviposition of B. tabaci in a concentration-

dependent manner. Such deterrent effects decreased in the case of

NeemAzalTS with residual age and were less severe in the greenhouse

compared to the laboratory environment.

Hatching of WF eggs was reduced by all three products both under lab and in

theGH. With increasing age of residues, hatch rates increased. This is probably

the result of decreasing activity of neem, abamectin and spinosad residues on

the plants. However, the intensity of reduction varied in all three cases. It

progressed rapidly in case of NeemAzalU, but was slower with spinosad and

lowest with abamectin. The results are in agreement with studies reported by

Premachandra et al. (2005) dealing with the thrips, Ceratothripoides clarathris,

a major pest on tomatoes in Thailand.

All three products caused heavy residual mortality of the immature stages of the

B. tabaci. Abamectin had the strongest performance and consequently caused

100% immature mortality at all residue levels followed by spinosad and

NeemAzalTS. The higher persistency of spinosad and abamectin was reported

also by Horowitz et al. (1997) and Premachandra et al. (2005). Whereas,

abamectin showed nearly no loss of activity with time under the greenhouse

conditions, toxicity of spinosad to immatures slightly decreased from 95% of

fresh residues to 91% 15-d post application and same aged residues caused

87% mortality under greenhouse conditions. Concentrations of 5, 10 and 20 ml/

20 l water for spinosad caused 100% mortality at larval instars and adult of the

Cetraothripoides claratis until 7-days post application under greenhouse

condition indicating the very strong persistency (Premachandra et al. 2005).

Similarly, in greenhouse experiments with cucumber and tomatoes, Narocka

(2002) recorded 100% mortality in western flower thrips, F. occidentalis at two

spinosad concentrations. In addition, persistent toxicity of spinosad was

reported from other economically important insect-pests, e.g. diamond back

moth (Hill and Foster 2000), Cabbage looper Trichoplusia ni (Hubner)


(Lepidoptera: Noctuidae) (Liu et al. 1999) and Caribbean fruit fly, Anastrepha

suspensa (Loew) (Diptera: Tephritidae) (King and Hennessey 1996) and the

eggplant flea beetle (Coleoptera: Chrysomelidae) on eggplants under field

conditions (McLeod et al. 2002). In contrast, neem�s toxicity decreased rapidly

already 5-d post application in the greenhouse and mortality rates dropped to

the level of control. This finding with neem is in line with work of Ascher et al

(2000). In a similar neem bioassay against F. occidentalis, under laboratory

conditions, residues of 0.1% Neemix-45 on cotton seedling were highly active

for 10-11 days but only 5 and 3-4 d in the greenhouse and outside, respectively.

The consistent progressive loss of activity with time more in the greenhouse

compared to the laboratory could be explained by the more rapid degradation of

the neem on exposure to sunlight, high temperatures and UV (Barnaby et al.

1989, Stokes and Redfern 1982, Johnson et al. 2003).

Conclusion In summary, our studies indicate that B. tabaci is highly susceptible to

NeemAzalTS spinosad and abamectin. However, the susceptibility varies with

WF growth stage and time span between application and infestation as well as

the presence and absence of sunlight. Spinosad affects adult WF but failed to

reduce egg deposition. However, it affects egg hatching, causing high immature

mortality and inhibiting adult emergence. Abamectin affects colonization, egg

deposition, egg hatch and induces high mortality amongst immatures. Neem

affects settling, egg deposition and egg hatch, as well as larval and pupal

mortality; but the chemical shows the strongest sensitivity and loss of activity

over time if exposed to adverse conditions (high temperature and intensive UV

radiation).

The use of neem products can help to control the serious pest B. tabaci in a

more safe and sustainable manner; particularly if only short term effects are

necessary since remigration of the pest, e.g. in GH, is low. However it easily

becomes ineffective in the presence of high temperature and strong ultra-violet

light (Johnson et al. 2003). Thus, we foresee that WF management in tropically

adapted greenhouses, if necessary for longer periods under heavy infestation

pressure, cannot be achieved with this botanical alone. It requires a

combination of neem and other safe products like spinosad or even abamectin,

if there is a need for product rotation to avoid resistance selection. The highly


efficient spinosad seems to be at risk of rapid selection of resistant biotypes if it

is used frequently (Zhao et al. 2002). Moreover, the possible combination of bio-

pesticides, with release of natural enemies, should be studied in more detail.

That requires reliable data about possible side effects under practical growing

conditions. Data so far available does not give a clear picture. Jones et al.

(2005) found spinosad to be highly toxic for Encarsia spp; but in another study

Zchori-Fein et al. (1994) combined abamectin and Encarsia for integrated

management of the WF. Therefore, in ongoing studies, we will elucidate

possible side-effects of these chemicals on the indigenous parasitoids of B.

tabaci in the humid tropics.

Impact of UV blocked GH on pest status of whiteflies, thrips and aphids 72

5. Impact of UV-blocking plastic covers and netting on the pest status

of Bemisia tabaci Gennadius (Homoptera: Aleyrodidae), Ceratothripoides claratris Shumsher (Thysanoptera: Thripidae) and Aphis gossypii Glover (Homoptera: Aphididae) on tomatoes in the humid tropics9

5.1. Introduction

Tomato production under protected cultivation in the humid tropics is extremely

vulnerable to abiotic stresses (temperature, humidity, air flow etc.) (Ajwang et

al. 2002), and to biotic stresses represented by insects (whitefly, thrips, aphids)

and, less directly, plant virus diseases vectored by these insects (Thongrit et

al.1986, Attathom et al. 1990, Premachandra et al. 2005). The damage that

whitefly (WF) inflicts on the host plant results from sap sucking, the heavy

deposition of honeydew, plant disorders like uneven ripening (Schuster et al.

1990) and spread of diseases caused by 50-60 different kinds of geminiviruses

(Markham et al. 1994, Brown et al. 1995). Similarly, thrips (Ceratothripoides

claratris Shumsher; Thysanoptera: Thripidae) is a serious pest species

attacking field- and greenhouse-grown tomatoes in Thailand (Premachandra et

al. 2005). Major damage is caused directly by mechanical damage through

feeding and oviposition and indirectly by transmitting tospoviruses (Murai et al.

2000, McMichael et al. 2002, Premachandra et al. 2005). Aphids, Aphis

gossypii (Homoptera: Aphididae) is another pest of tomato in Thailand causing

direct damage by sucking plant sap and reducing the overall quality and

productivity. Often plants are attacked by a complex of these pests which can

potentate direct damage and lead to detrimental infections by more then one

type of virus (Summers et al. 2004).

Chemical control is the primary method to manage WF, thrips and aphids

however management using pesticides has not been effective, provides only

partial control (Denholm et al. 1996, Horowitz and Ishaaya 1996) or fails mainly

9 To be published as Kumar, P., and H-M. Poehling. Impact of UV-blocking plastic covers and netting on the pest status of Bemisia tabaci Gennadius (Homoptera: Aleyrodidae), Ceratothripoides claratris Shumsher (Thysanoptera: Thripidae) and Aphis gossypii Glover (Homoptera: Aphididae) on tomatoes in the humid tropics. Submitteted to Enviornmental Entomology.

5


because of rapid selection of resistant pest biotypes of WF (Denholm et al.

1996, Prabhaker et al. 1998, Cahill et al. 1995, Elbert and Nauen 2000), thrips

(Kontsedalov et al. 1998, Espinosa et al. 2002), or aphids (Foster et al. 2000).

Botanicals like neem can be efficient with lower risk of resistance selection (e.g.

Thoeming et al 2003, Kumar et al. 2005) but suffer from rapid dissipation and

degradation in presence of UV light under tropical conditions, which reduces

persistency (Barnby et al. 1989, Johnson et al. 2003, Barrek et al. 2004).

Some species of insects like WF, thrips and aphids have been shown to be

dependent on UV light (mainly UV A from 320 � 400 nm) to orient themselves

during flight. These species may use UV-light reflectance patterns as cues for

recognizing host plants and flower species (Kring 1972, Rossel and Wehner

1984, Scherer and Kolb 1987, Greenough et al. 1990, Kring and Schuster 1992,

Goldsmith 1993, Costa and Robb 1999). Furthermore, previous findings show

that Bemisia argentifolii and Frankliniella occidentalis are attracted to UV light

(Mound 1962, Matteson and Terry 1992, Antignus et al. 1996, Antignus 2000).

Similarly reduced aphid movement and delayed spread of aphid-borne virus

diseases were achieved by using UV-blocking plastic mulches for squash and

other crops (Brown et al. 1993, Summers and Stapleton 1998, Stapleton and

Summers 2002). Field studies from Israel demonstrated a significant reduction

in crop infestation by B. tabaci, aphids and thrips when UV- blocking plastics

were used as greenhouse covers (Antignus et al. 1996, 1998, 2001, Antignus

2000). These materials are also reported to reduce the incidence of WF

transmitted geminiviruses.

The area under protected cultivation in the tropics is on the rise. This trend is

complemented by the constant change and improvement in existing covering

materials and other production technologies in the last decades, and consumer

demand for safe food has encouraged growers in the tropics to shift towards

protected cultivation (Giacomelli and Roberts 1993, Ashekanzi 1996). The aim

of protected cultivation is not only to allow production under otherwise adverse

climatic conditions (e.g. heavy rainfalls) but to reduce dependency on frequent

pesticide use with all its drawbacks (e.g. residues, operator health, increased

production costs and resistance. However, the use of screens as a physical

means of control has limitations, particularly with small insects since very small

mesh size in nets, or complete cover with plastics, reduces the efficiency of


natural ventilation. Good ventilation is a prerequisite for greenhouses without

expensive cooling devices (Michelle and Baker 2000, Ajwang et al. 2002).

Materials hindering insect invasion but permitting adequate ventilation are

desired. UV-blocking materials may be a further advance in greenhouse

development. All past studies like those of Antignus (1998, 2000) and others

mentioned-above reported the use of UV-blocking nets/screen or plastics alone,

and their efficiency in reducing immigration, dispersal and virus infection.

However, none of these studies were performed under the conditions of the

humid tropics, where a combination of rain blocking plastic roof materials and

well ventilated side wall covers is necessary to allow year round production of

sensitive vegetable such as tomatoes. Therefore, we undertook this study with

different combined UV-blocking and UV-transmissible roof and wall materials in

small experimental greenhouses to study the movement pattern of the more

serious small plant sucking insects (WF, thrips and aphids) of tomatoes, and the

incidence of viruses transmitted by these vectors in the humid tropics.

5.2 Materials and Methods Location

The study was part of an interdisciplinary research project funded by the




(Solanaceae), cv. King Kong II) at the greenhouse complex provided for the

AIT-Hanover Project, Asian Institute of Technology, Bangkok, Thailand. The

experiments were conducted during the later part of the spring (March) until end

of rainy season (October) 2005.


Nets & Plastics

Two nets; UV-blocking, Bionet® and non UV-blocking (= UV transmitting), Anti

Insect® nets (50 mesh: Polysack Plastic Industries, Israel) along with two

plastics, UV-blocking (Sun Selector Diffused Antivirus®, Ginegar Plastic Product

Ltd, Kibbutz, Israel) and UV-transmitting (= non blocking) plastic film, PE-1A

(RKW AG, Germany) were used in the experiments. The spectral transmission

properties of these films were analyzed using a PerkinElmer Lambda 900 UV/

VIS/NIR spectrophotometer (PerkinElmer Life and Analytical Sciences, Boston,

MA) (see fig. 5.1).

Fig 5.1. Spectral transmissivity of UV-blocking plastic film (A, Sun Selector Diffused Anti Virus®, Ginegar Plastic Products Ltd., Israel), UV-transmitting plastic, PE-1A (B, RKW AG, Germany),UV blocking net (C, Bionet®,Polysack, Israel) and UV-transmitting nets (D, Anti-Insect®, Polysack, Israel) films measured with a PerkinElmer Lambda 900 UV/VIS/NIR spectrophotometer.

(A)

0

10

20

30

40

50

60

70

80

90

100

300 400 500 600 700 800Wavelength (nm)

Tran

smis

sion

(%)

(B)

0

10

20

30

40

50

60

70

80

90

100

300 400 500 600 700 800Wavelength (nm)

Tran

smis

sion

(%)

(C)

0

10

20

30

40

50

60

70

80

90

100

300 400 500 600 700Wavelength (nm)

Tran

smis

sion

(%)

(D)

0

10

20

30

40

50

60

70

80

90

100

300 400 500 600 700Wavelength (nm)

Tran

smis

sion

(%)


Treatments and greenhouses

These two nets (UV-blocking and non UV-blocking; henceforth will be referred

as UVB-N and NUVB-N, respectively) and plastics (UV-blocking and non-

blocking; henceforth will be referred as UVB-P and NUVB-P, respectively) were

permutated in 4 different combinations: UV blocking nets + UV blocking Plastics

[henceforth referred as B (N+P)]; Non UV-blocking net + UV blocking plastic

[NB-(N+BP)]; UV blocking nets + UV non-blocking Plastics [ BN+N-BP)]; UV

Non-blocking nets + UV non-blocking plastic [NB (N+P)]. A total of eight

greenhouses (GH) (7.5 m x 2 m x 2 m) were constructed with four GH each

placed in identical orientations (either east/west or north/south direction) to

avoid any effect of orientation. Furthermore, each greenhouse was provided

with two identical doors at the length side. The front and rear end of the door

walls were covered with identical nets used for the sidewalls of each

greenhouse. The sidewalls of the greenhouses were always covered with either

of the nets and the roofs with either of the plastics. Between GH, 1.5 meter

space reduced shading from each other. The area around the GH complex was

cleaned and all weed plants were removed prior to each series of experiments.

Two replications of each treatment were arranged in a complete randomized

block design. Between each series, greenhouses were thoroughly washed and

cleaned approximately one week prior to new experiments. A total of 2

experimental series each of 6 weeks duration were carried out and each

experiment was repeated once over the time. Data collection started one week

after transplanting for 5 more weeks. A total of 30 potted (25 cm high and 27 cm

Ø) tomato plants (2 weeks old) were transplanted in a commercial local media

composed of clay, sand, and silt in proportions of 31, 30 and 39%, respectively,

and 29% of organic matter. Tomato seedlings were grown in an insect free

evapo-cooled nursery. Radiation triggered and scheduled drip irrigation

combined with dosatron fertigation was provided to ensure the mineral balance

and optimal growth and development of the tomatoes. Each GH was provided

with a temperature, humidity and UV-A using Radiometer UV-Sensor (Dr.

Grobel UV-Elektronik GmbH, Germany).


CaCV detection by DAS-ELISA

Double Antibody Sandwich Enzyme-Linked Immunosorbent Assay (DAS-

ELISA) was conducted for the confirmation of CaCV-AIT infection of tomato

plants in addition to symptom diagnostics. Polyclonal and monoclonal

antibodies raised against N-protein of Watermelon Silver Mottle Virus (WSMV)

and Groundnut Bud Necrosis Virus (GBNV) (Agdia, Inc., Elkhart, ID, USA) were

used. Plant leaves were homogenized at a ratio of 1: 5 in PBS-T (2.5 mM KCl, 1

mM KH2PO4, 8 mM Na2HPO4, 0.14 M NaCl and 0.6 ml/l Tween 20) containing

0.45 polyvinylpyrollidone (PVP). Leaves from healthy plants were used for the

control treatment. Absorbance values were read with a microplate reader (BIO-

Tek Instruments, Inc, Vermont, USA) at 405 nm, with PBS-T as a blank. The

absorbance values were corrected by subtracting the average of three wells of

the blank from samples means. Samples having absorbance means three times

that of the control was considered as positive. For other viruses e.g. Tomato

Yellow Leaf Curl Virus (TYLCV) visual counts were made on the basis of

symptoms only.

Experiment 1 and 2. Effect of UV blocking nets and plastics on the

immigration of whitefly, thrips and aphids and occurrence of tospoviruses

and TYLCV (reduced ventilation by partly open doors) Two rounds of experiment, were conducted using above-mentioned set ups of

the 8 GH. The two parallel doors of the GH were simultaneously opened every

morning from 6.00-10.00 am (partial ventilation), coinciding with the peak

insect�s activities time (Cohen and Melamed-Madjar 1978). The immigrating WF

population were measured by yellow sticky traps (YST) (25 x 15 cm) positioned

half at the plant canopy and half above canopy. The YST were made from

yellow PVC sheets coated with insect-glue (Kosfix®, Kosmix Polymer, Bangkok,

Thailand) on both sides. A total of 6 YST were placed for each GH, changed

once a week and number of WF trapped at both side of the traps were counted.

Each trap was considered as one replication and this way a total of 5 weekly

readings were collected on the WF entering inside each of 8 GH during each

experiment. Similarly, the numbers of adult WF per plants were counted by

selecting one young fully developed leave per plant, gently turning it over and

visually counting the number of adults present on the lower surface. The


counting was carried out in the early morning (7.00 am and before) from 3

randomly selected plants from each greenhouse.

Similarly, once a week, number of thrips entering in each GH was counted

using Blue Sticky Traps (BST) of same dimension simultaneously with YST (12

replications). Additionally, once a week number of thrips infested leaves were

counted from 3 pre-marked plants until the fifth week to asses cumulative

weakly leaf damage. Once a week, number of virus infected tomato plants were

counted and marked and towards the end of the experiments at 35 days after

transplanting (DAT), DAS-ELISA tests were carried out to distinguish between

the tospovirus and other viruses e.g. TYLCV. Since the tospovirus was the most

commonly occurring one, the plants failed to test positive for the CaCV-AIT

infection but showing virus symptoms were assumed to be infected with the

TYCLV.

The number of immigrating winged aphids was monitored using same YST

placed for the WF monitoring in similar manner as explained above. The

immatures and wingless adults (henceforth will be refereed as immatures) were

counted by selecting one young, fully expanded leaf per plant, gently turning it

over and visually counting their numbers present on the lower surface.

Experiment 3 and 4. Effect of UV blocking nets and plastics on the

immigration and attraction of whitefly, thrips and aphids and occurrence

of tospoviruses and TYLCV (full ventilation with complete open doors) Two rounds of experiments (June � July; August - September) were carried out

in a similar GH set-up as discussed above with a single exception of timing of

GH door opening. Two GH doors were kept open during the entire period of

experiment (full ventilation). The numbers of WF and thrips were counted on the

YST and BST as per the procedure explained above (weekly until 35 DAT).

Similarly, number of thrips infested leaves and virus infected plants were

counted, marked and plant viruses were monitored. Simultaneously with these 2

rounds of experiments, ability of WF and thrips to reach to the experimental GH

were studied by attaching two YST and BST each at the outer walls (centrally

placed). Traps were changed weekly followed by counting of thrips and WF.

The position and orientation of the traps on all 4 GH types were similar.


Data Analyses

Adult whiteflies, thrips and aphids on traps, alate aphids & whiteflies on leaves,

number of thrips infested leaves, percentage of virus infected plants were

subjected to HOVTEST = LEVENE option of SAS to account for homogeneity of

variance and normality. In case of non-homogeneity, percent values were

transformed using arcsine�square-root (arcsin√) transformation. Insects on

traps and plants and number of infested leaves count values were transformed

by square-root (√) transformation before running an ANOVA followed by mean

separation using Fisher�s LSD test (Steel and Torrie 1980, Gomez and Gomez

1984). Data were then back transformed for presentation as Mean±SE. A

significance level of ∝ = 0.05 was used in for all analysis.

5.3 Results Light Transmission and Temperature. No significant differences in

temperatures and humidity inside the four tunnels were found during all 4

experiments. However, the UV light intensity varies under each GH type either

during sunny and cloudy days during each four experiments (see figure 5.2).

The UV levels drop to almost half during cloudy days. During experiments 1 and

2, approximately 20% of the 5 weeks long experiments were cloudy whereas it

was approximately 40% during experiments 3 and 4.


Time (600 - 1800 h)

06:00 10:00 14:00 18:00

UV

mea

sure

men

t (w

m-2

)

0

2

4

6

8

10

12

14 B (N+P)-S* B (N+P)-C** NB(N+P)-S NB (N+P)-C B-N+NB-P-S B-N+NB-P-C NB-N+B-P-S NB-N+B-P-C

*S = Sunny Day**C = Cloudy day

Fig. 5.2. UV-A measurement (wm-2) under each four greenhouses, UV-blocking net sidewalls with UV-blocking plastic film as roof [B (N+P)]; UV non-blocking nets as sidewalls and UV non blocking plastic films as roof [NB (N+P)]; UV-blocking nets as side walls and UV non blocking plastic films as roof [B-N+NB-P]; and, UV non blocking nets as side wall and UV-blocking plastics films as roof [NB-N+B-P] using Radiometer UV-Sensor (Dr. Grobel UV-Elektronik GmbH, Germany).


Experiment 1 and 2. Partial Ventilation

Whitefly. Significantly fewer whiteflies entered into the B (N+P) GH type

compared to the other tested combinations during all sampling days (or

periods). WF always preferred to enter the NB (N+P) GH type, irrespective of

either initial low population (exp. 1) or at relatively higher population (exp. 2)

(table 1). Comparing the other combinations, WF preferred to enter GHs with

roofs made from the non-blocking plastics. In contrast, GHs with UV blocking

plastic roofs had significantly lower number of WF on YST inside. Moreover,

colonization was clearly related to the sidewall net properties (see table 5.1).

Similarly, significantly fewer adult WF were recorded on leaves in the B (N+P)

GH compared to the other tested GH types. Highest numbers of WF per leaf

were recorded from the NB (N+P) type GH (see table 5.1). During the second

round of experiments settling of WF followed the same trends (see table 5.2).

Table 5.1. Weekly mean (±SE) number of Bemisia tabaci adults per leaf and on yellow sticky traps trapped inside GH during experiment 1.

Treatments Days After Transplanting B (N+P) NB-N+ B-P B-N+ NB-P NB (N+P) WF per leaf

7 0.00±0.00a 0.50±0.22b 2.50±0.34c 5.00±0.86d 14 0.00±0.00a 0.83±0.40ab 2.00±0.52b 10.33±1.65c 21 0.17±0.17a 1.50±0.22b 5.67±0.71c 15.50±2.28d 28 0.50±0.34a 2.00±0.45a 7.67±1.86b 22.17±3.12c 35 1.50±0.43a 2.83±0.54a 10.00±2.14b 22.67±2.54c

WF per YST 7 0.00±0.00a 0.42±0.15b 1.83±0.37c 8.92±1.04d

14 0.17±0.11a 1.00±0.28a 6.75±0.45b 24.83±4.31c 21 0.75±0.41a 2.58±0.56b 10.58±0.69c 25.17±1.97d 28 0.92±0.26a 1.42±0.38a 11.58±0.68b 32.58±3.59c 35 0.08±0.08a 1.92±0.47b 7.50±1.14c 28.58±3.84d

ANOVA for each DAT was performed followed by mean separation using Fisher�s LSD

test. Means within DAT followed by the same letter (s) are not significantly different at

P = 0.05.


Table 5.2. Weekly mean (±SE) number of Bemisia tabaci adults per leaf and on yellow sticky traps trapped inside GH during experiment 2.

Treatments Days After Transplanting B (N+P) NB-N+B-P B-N+NB-P NB (N+P) WF per leaf

7 0.00±0.00a 0.67±0.21b 2.83±0.40c 6.50±1.52d 14 0.00±0.00a 0.83±0.40a 4.33±0.21b 19.33±3.63c 21 0.17±0.17a 2.33±0.33b 7.50±1.06c 30.67±7.79d 28 0.83±0.48a 3.50±0.76b 9.67±1.31c 29.00±4.43d 35 1.50±0.34a 2.33±0.42a 11.17±2.14b 34.67±6.29c

WF per YST 7 0.00±0.00a 0.42±0.19a 1.58±0.56b 10.75±1.04c

14 0.17±0.11a 2.58±0.66b 10.67±1.36c 33.33±1.97d 21 0.33±0.22a 1.17±0.39a 6.75±0.86b 47.25±4.26c 28 0.42±0.26a 1.92±0.61b 9.75±1.58c 71.92±5.09d 35 0.08±0.08a 5.25±0.87b 20.00±1.56c 93.17±5.68d



P = 0.05.

Aphids. Winged aphids followed the same entry trends as WF and significantly

less aphids were trapped inside the B (N+P) GH compared to other tested

treatments (see table 5.3 and 5.4). On 35 DAT both during exp. 1 and 2, highest

counts were recorded on the YST. Moreover, for most sampling dates no

significant differences were recorded inside B (N+P) and NB-N+B-P type GH.

Significantly higher numbers of aphids per leaf were counted within the GH with

more UV light intensity during both experimental periods (see table 5.3 and 5.4).

It is obvious from the results that winged aphids preferred to immigrate into

more UV receiving GH compared to the ones with less UV and that denser

immatures and wingless adult populations developed on the leaves. Thus the

GH made from the B (N+P) provided the best protection against the winged as

well as the immature aphids.


Table 5.3. Weekly mean (±SE) number of wingless adults and immatures aphids per leaf and winged aphid adults trapped on yellow sticky traps inside during experiment 1.

Treatments Days After Transplanting B (N+P) NB-N+ B-P B-N+NB-P NB (N+P)

Immatures and wingless adults per leaf 7 0.17±0.17a 0.17±0.17a 0.50±0.22a 4.00±0.63b

14 0.00±0.00a 1.33±0.33b 3.50±0.81c 12.00±2.54d 21 0.00±0.00a 0.50±0.22a 4.50±0.56b 15.17±3.72c 28 0.00±0.00a 0.17±0.17a 1.33±0.33b 6.67±0.99c 35 0.00±0.00a 0.50±0.22a 3.17±0.79b 7.83±0.17c

Winged adults per YST 7 0.00±0.00a 0.00±0.00a 0.75±0.18b 6.08±1.87c

14 0.50±0.19a 1.00±0.35a 3.47±0.42b 10.83±1.09c 21 0.17±0.11a 1.42±0.42b 3.92±0.81c 12.83±1.64d 28 0.42±0.19a 0.67±0.22a 4.75±0.79b 14.50±2.18c 35 0.25±0.13a 0.75±0.18b 3.92±0.71c 15.92±0.90d



P = 0.05.

Table 5. 4. Weekly mean (±SE) number of wingless adults and immatures aphids per leaf and winged aphid adults trapped on yellow sticky traps inside GH during experiment 2.

Treatments Days After

Transplanting B (N+P) NB-N+ B-P B-N+NB-P NB(N+P)

Immatures and wingless adults per leaf 7 0.00±0.00a 0.00±0.00a 1.50±0.50b 4.17±0.70c

14 0.17±0.17a 1.00±0.37ab 2.67±0.95b 6.50±0.56c 21 0.00±0.00a 0.83±0.40b 2.33±0.80c 7.17±0.54d 28 0.17±0.17a 0.83±0.40a 2.83±0.60b 8.17±0.60c 35 0.00±0.00a 0.67±0.33b 2.50±0.43c 9.33±0.61d

Winged adults per YST 7 0.00±0.00a 0.00±0.00a 1.08±0.73b 5.08±1.37c

14 0.25±0.13a 0.67±0.22a 4.17±0.95b 11.58±2.76c 21 0.00±0.00a 1.75±0.98b 5.08±1.47c 15.00±2.92d 28 0.67±0.22a 1.58±0.73a 6.42±2.26b 21.33±3.92c 35 0.33±0.22a 2.33±0.92a 9.67±1.71b 25.92±4.29c



P = 0.05.


Thrips and leaf damage. Thrips was the most recorded pest and immigration

followed similar trends that of WF and aphids. NB (N+P) GH attracted

significantly the highest number of thrips compared to all other GH types (see

table 5.5). During second round of experiments, more thrips per BST and more

thrips damaged leaves were recorded. At 35 DAT, 162 and 176 thrips per BST

were recorded under the NB (N+P) material during experiment 1 and 2

respectively against 0 and 3.75 thrips during same period inside B (N+P) GH

types. For over 3 weeks significant differences in numbers of thrips were

recorded inside B (N+P) and NB-N+B-P type GH during experiment 1 and 2.

The higher number of immigrating thrips inside the NB (N+P) caused

significantly higher cumulative number of thrips infested leaves (leaf damage) at

35 DAT compared to the other greenhouses (see table 5.5 and 5.6).

Table 5.5. Weekly mean (±SE) number of adult thrips per BST trapped inside GH and cumulative leaf damage during experiment1.

Treatments Days After Transplanting B (N+P) NB- N+ B-P B-N+NB-P NB (N+P) Adult per BST

7 0.00±0.00a 0.00±0.00a 0.25±0.13a 9.75±0.75b 14 0.25±0.13a 0.67±0.22a 6.75±1.08b 17.42±1.99c 21 0.17±0.11a 1.00±0.35b 11.50±0.89c 33.42±1.59d 28 0.42±0.19a 1.58±0.31b 20.00±0.83c 72.83±4.52d 35 0.00±0.00a 1.75±0.48b 24.08±0.54c 162.67±2.25d

Cumulative no thrips infested leaves/plant 7 0.00±0.00a 0.67±0.21b 1.00±0.45b 2.00±0.26c

14 0.33±0.21a 1.17±0.40ab 2.17±0.70b 5.17±0.31c 21 0.83±0.31a 1.50±0.50a 3.50±0.72b 9.50±0.34c 28 1.33±0.61a 2.17±0.40ab 4.83±1.17b 12.67±0.33c 35 1.67±0.71a 2.83±0.60a 7.00±1.34b 13.33±0.49c



P = 0.05.


Table 5.6. Weekly mean (±SE) number of adult thrips per BST trapped inside GH and cumulative leaf damage during experiment 2.

Treatments Days After Transplanting B (N+P) NB-N+B-P B-N+NB-P NB (N+P) Adult per BST

7 0.25±0.13a 0.58±0.23a 3.75±0.64b 18.00±1.35c 14 0.17±0.11a 0.75±0.33a 7.67±0.54b 20.08±1.79c 21 0.33±0.14a 1.92±0.42b 17.25±0.99c 53.33±1.45d 28 0.92±0.26a 5.08±0.77b 23.08±1.53c 114.33±4.65d 35 3.75±0.37a 10.92±1.60b 33.50±1.51c 176.75±6.05d

Cumulative no thrips infested leaves/plant 7 0.00±0.00a 0.50±0.22ab 1.17±0.54b 3.33±0.76c

14 0.33±0.21a 1.17±0.48ab 3.00±0.89b 8.33±0.67c 21 0.83±0.40a 1.33±0.56a 4.17±0.79b 10.17±0.60c 28 1.67±0.61a 2.50±0.62b 5.00±1.00c 13.83±0.48d 35 1.83±0.54a 3.00±0.73b 5.67±1.23c 14.50±0.34d



P = 0.05.

Virus spread. Cumulative percent virus incidence at 35 DAT was significantly

lower with 5.0% recorded inside B (N+P) GH compared to 45 % under NB

(N+P) GH types (F = 29.80; df= 3, 7; P = 0.0034) (see fig. 5.3 A). Tospovirus

constituted the major proportion and reached 88% and 66% respectively in B

(N+P) and NB (N+P) greenhouse types (see fig 5.4 A) . Inside the NB (N+P)

GH, first virus infected plants were recorded earlier and virus spread at faster

rates, compared to the B (N+P) GH. During the second round of experiments,

more plants showed virus symptoms but similar to the first experiment virus

spread was significantly higher under NB (N+P) GH (F = 243.73; df= 3, 7; P =

0.0001) (see fig.5.3 B) compared to B (N+P) type GH. However no significant

differences were found in B (N+P) and NB-N+B-P types GH. Out of these a total

of 83.33 % plants were tested positive for the tospovirus (see fig 5.4 B). Percent

cumulative infestation with tospovirus was significantly higher under the NB

(N+P) type GH (F = 24.30; df= 3, 7; P = 0.005). Similar to the experiment 1,

virus incidence started earlier at 14 DAT under the NB (N+P) GH types

compared to 28 DAT under B (N+P) GH types. During both experiment 1 and 2

under the UV blocking plastic GH roof, most of the virus affected plants were

found near to the doors, whereas in GH with UV non-blocking roof, infected

plant were dispersed all over the GH. The results clearly indicate that the B

(N+P) GH type provided the best protection against the virus infection.


Fig. 5.3. Percent cumulative virus infected tomato plants under greenhouses, UV-blocking net sidewalls with UV-blocking plastic film as roof [B (N+P)]; UV non-blocking nets as sidewalls and UV non blocking plastic films as roof [NB (N+P)]; UV-blocking nets as side walls and UV non blocking plastic films as roof [B-N+NB-P]; and, UV non blocking nets as side wall and UV-blocking plastics films as roof [NB-N+B-P], (A) during experiment 1 and (B) experiment 2, when greenhouse door was open for 6.00-10.00h. Cumulative percent at 35 days after transplanting sharing a common letter are not significantly different at P <0.05, Fisher’s LSD.

(A )

Cum

ulat

ive

% (±

SE) v

irus

infe

cted

pla

nts

0

2 0

4 0

6 0

8 0

1 0 0B (N + P ) N B -N + B -P B - N + N B -P N B (N + P )

a

b

cb c

D a y s A fte r T ra n s p la n t in g (D A T )0 1 0 2 0 3 0 4 0

Cum

ulat

ive

% (±

SE

) viru

s in

fect

ed p

lant

s

0

2 0

4 0

6 0

8 0

1 0 0(B )

a

b

cc


Fig. 5.4. Proportion of tospovirus in comparison of total virus infected tomato plants under different greenhouses, UV-blocking net sidewalls with UV-blocking plastic film as roof [ B (N+P)]; UV non-blocking nets as sidewalls and UV non blocking plastic films as roof [NB (N+P)]; UV-blocking nets as side walls and UV non blocking plastic films as roof [B-N+NB-P]; and, UV non blocking nets as side wall and UV-blocking plastics films as roof [NB-N+B-P] during experiment 1 (A) and experiment 2 (B), when greenhouse doors open for 600-1000 h (partial ventilation). Bars sharing a common letter are not significantly different at P < 0.05, Fisher’s LSD.

T r e a t m e n tB ( N + P ) N B - N + B - P B - N + N B - P N B ( N + P )

umul

ativ

e %

(Mea

n+SE

) Tot

al a

nd T

ospo

Viru

s in

fest

ed to

mat

o p

0

2 0

4 0

6 0

8 0

ab

c

c

aa b

b

d

( B )

( A )

Cum

ulat

ive

% (M

ean+

SE) T

otal

and

Tos

po V

irus

infe

sted

tom

ato

plan

t

0

2 0

4 0

6 0

8 0

T o t a l - V i r u s T o s p o V i r u s

aa b

b

c

aa

b

c


Experiment 3 and 4. Complete Ventilation

Whitefly. In total, a higher WF population was observed when gates were kept

open to achieve complete ventilation. Similar to the entry trends under partial

ventilation, significantly fewer number of WF entered inside the B (N+P) GH

compared to other tested combinations during all sampling periods. Similar to

the lower number trapped on YST, significantly fewer WF were found on leaves

under B (N+P) GH over the sampling period (see table 5.7). These results yet

again indicated the preference of WF to immigrate into to UV rich environment

irrespective of the ventilation status under NB (N+P) type GH. During the

second round of experiments entry and settling of WF followed the same trends

(see table 8). The load of WF measured at outside walls of the NB (N+P) were

significantly higher in either rounds of the experiments 3 and 4 (see table 5.7

and 5.8 respectively) compared to B (N+P) GH types.

Table 5. 7. Weekly mean (±SE) number of Bemisia tabaci adult per leaf, on yellow sticky traps trapped inside GH and trapped on the yellow sticky traps on the outer walls of the GH during experiment 3.


Transplanting B (N+P) NB-N+ B-P B-N+NB-P NB (N+P)

WF per leaf 7 0.17±0.17a 0.50±0.22a 4.33±1.65b 15.17±2.21c

14 2.17±0.48a 3.00±0.37a 9.50±1.63b 37.50±3.80c 21 2.33±0.21a 3.50±0.62a 18.67±1.78b 53.67±9.04c 28 2.67±0.56a 4.00±0.37a 20.17±1.72b 60.00±9.15c 35 3.83±0.54a 5.17±1.01a 15.17±1.76b 36.00±2.18c

WF per YST Inside 7 1.00±0.33a 2.25±0.39ab 4.92±0.34b 15.00±4.49c


WF per YST trapped on outer wall of GH 7 1.00±0.42a 1.63±0.60a 4.00±0.68b 22.63±2.90c




P = 0.05.


Table 5.8. Weekly mean (±SE) number of Bemisia tabaci adult per leaf, on yellow sticky traps trapped inside GH and trapped on the yellow sticky traps on the outer walls of the GH during experiment 4.

Treatments Days after

Transplanting B (N+P) NB-N+B-P B- N+ NB-P NB (N+P)

WF per leaf 7 0.17±0.17a 0.67±0.33a 5.00±1.39b 17.17±2.69c

14 2.17±0.60a 3.33±0.67a 10.33±0.92b 38.50±5.85c 21 1.67±0.61a 3.50±0.76ab 5.83±0.60b 24.17±4.61c 28 2.33±0.33a 2.17±0.60a 6.67±1.12b 22.17±3.67c 35 2.17±0.31a 3.67±0.56a 6.33±0.84b 18.50±2.78c

WF per YST tapped inside GH 7 2.75±0.48a 4.49±0.50a 10.17±0.27b 21.33±3.02c

14 5.33±0.99a 7.67±0.45a 17.42±0.56b 50.00±6.28c 21 5.93±0.84a 7.33±0.83a 20.50±1.02b 52.58±4.09c 28 4.58±1.33a 11.75±0.62b 36.50±1.80c 98.75±11.99d 35 6.83±0.81a 10.75±0.68b 31.50±1.34c 90.92±7.69d

WF per YST trapped on outer walls of GH 7 2.00±0.46a 4.13±0.64a 6.00±1.02b 17.50±2.27c

14 3.88±0.81a 5.63±0.53a 13.25±0.67b 35.00±3.26c 21 3.63±0.91a 5.38±0.60a 12.63±2.02b 30.88±1.54c 28 3.38±0.56a 5.88±0.52b 11.13±0.97c 43.63±2.56d 35 3.13±0.58a 6.50±0.19b 14.50±0.80c 35.38±1.25d



P = 0.05. Thrips and leaf damage. Again thrips was recorded as the most abundant pest

and similar to the previously observed trends, significantly higher number of

thrips entered and were trapped inside the NB (N+P) GH compared to other GH

combinations tested in both rounds of experiments (see table 9 and 10).

Moreover significantly higher cumulative leaf damage was observed under NB

(N+P) type GH (table 9 and 10). Thrips followed the same trends of entry and

attraction towards UV-rich environment and a higher number of thrips focused

on sidewalls of NB (N+P) type compared to B (N+P) type GH in either of the

two rounds of experiment (table 5.9 and 5.10).


Table 5.9. Weekly mean (±SE) number of thrips on blue sticky traps inside GH and trapped on the outer walls of the GH and cumulative leaf damage during experiment 3.


Transplanting B (N+P) NB-N+B-P B- N+ NB-P NB (N+P)

Thrips per BST trapped inside GH 7 3.33±0.66a 4.25±0.93a 16.83±1.70b 60.50±11.13c


Cumulative no thrips infested leaves/plant 7 0.33±0.21a 0.67±0.21a 1.50±0.22b 2.67±0.21b

14 1.33±0.33a 2.00±0.00b 4.17±0.31c 8.67±0.42d 21 1.67±0.42a 2.67±0.21b 5.83±0.40c 11.17±0.48d 28 1.83±0.48a 3.67±0.21b 8.17±0.40c 14.00±0.63d 35 2.33±0.33a 5.00±0.37b 11.33±0.33c 21.00±0.68d

Thrips per BST trapped on outer walls of GH 7 2.13±0.55a 2.50±0.33a 6.75±0.53b 19.88±1.41c




P = 0.05.


Table 5.10. Weekly mean (±SE) number of thrips on blue sticky traps inside GH and trapped on the outer walls of the GH and cumulative leaf damage during experiment 4.


Transplanting B (N+P) NB-N+ B-P B-N+NB-P NB(N+P)

Thrips per BST trapped inside GH 7 5.83±0.86a 11.25±1.32b 22.75±2.05c 61.42±7.58d

14 5.25±1.41a 15.50±1.28b 44.67±2.70c 145.25±12.12d 21 11.33±2.29a 25.42±2.72b 60.17±3.36c 190.92±21.30d 28 12.92±1.89a 24.42±2.67b 76.50±5.75c 296.67±21.09d 35 14.92±2.45a 23.58±3.75a 69.75±6.97b 376.33±23.77c

Cumulative no thrips infested leaves/plant 7 0.50±0.22a 0.83±0.31a 1.67±0.21b 2.33±0.33b

14 1.17±0.31a 2.33±0.21b 3.83±0.48ab 5.00±0.58c 21 1.33±0.33a 3.17±0.31b 5.67±0.61c 8.00±0.68d 28 2.00±0.52a 3.83±0.48b 8.50±0.67c 12.33±0.67d 35 2.83±0.48a 4.33±0.49b 10.67±0.92c 18.33±0.88d

Thrips per BST trapped on outer walls of GH 7 2.38±0.60a 5.25±1.44ab 11.63±2.06b 34.75±11.92c

14 4.50±0.91a 14.00±1.64b 28.63±2.21c 47.13±4.84d 21 5.00±0.60a 9.63±1.40a 29.75±0.96b 68.38±8.96c 28 6.00±1.86a 9.13±1.16a 21.50±2.04b 71.25±6.82c 35 2.75±0.73a 9.13±1.30b 17.13±1.42c 73.00±2.43d



P = 0.05.

Virus spread. Cumulative percent virus incidence at 35 DAT during exp. 3 was

8 % inside B (N+P) GH compared to 100% under NB (N+P) GH type (F =

1588.25; df= 3, 7; P = 0.0001) (see fig 5.5 A). Tospovirus constituted the major

proportion and reached over 75% infection level under B (N+P) GH type (F =

96.38; df= 3, 7; P = 0.0003) (see fig 5.6 A ). Similar to the trends reported with

the partial ventilation experiments, inside the NB (N+P) GH types, virus

symptoms appeared early and spread at a faster rate compared to B (N+P) GH

types. During second round of experiments, overall slightly less cumulative virus

incidence was recorded at 96% under NB (N+P) GH type with similar trends as

reported for the previous rounds (F = 196.94; df= 3, 7; P = 0.0001) (see fig. 5.5

B). Toppoviruses appeared in similar manner as of the experiment 3 (see fig 5.6

B) . Similarly the virus symptoms appeared earlier and then spread at faster

rates under NB (N+P) GH type over B (N+P) GH types.


Fig. 5.5. Percent cumulative virus infected tomato plants under greenhouses (treatments), UV-blocking net sidewalls with UV-blocking plastic film as roof [B (N+P)]; UV non-blocking nets as sidewalls and UV non blocking plastic films as roof [NB (N+P)]; UV-blocking nets as side walls and UV non blocking plastic films as roof [B-N+NB-P]; and, UV non blocking nets as side wall and UV-blocking plastics films as roof [NB-N+B-P], (A) during exp. 3 and (B), exp. 4, when greenhouse doors kept open (complete ventilation). Cumulative percent at 35 days after transplanting sharing a common letter are not significantly different at P <0.05, Fisher’s LSD.

Cum

ulat

ive

% (±

SE) v

irus

infe

cted

pla

nts

0

20

40

60

80

100B(N+P) NB-N+B-P B-N+NB-P NB(N+P)

a

b

cd

(A)

Days After Transplanting0 10 20 30 40

Cum

ulat

ive

% (±

SE

) viru

s in

fect

ed p

lant

s

0

20

40

60

80

100 (B)

cc

b

a


Fig. 5.6. Proportion of tospovirus in comparison of total virus infected tomato plants under different greenhouses (treatments), UV-blocking net sidewalls with UV-blocking plastic film as roof [ B (N+P)]; UV non-blocking nets as sidewalls and UV non blocking plastic films as roof [NB (N+P)]; UV-blocking nets as side walls and UV non blocking plastic films as roof [B-N+NB-P]; and, UV non blocking nets as side wall and UV-blocking plastics films as roof [NB-N+B-P] during experiment 3 (A) and exp. 4 (B), when greenhouse doors kept open (complete ventilation). Bars sharing a common letter are not significantly different at P <0.05, Fisher’s LSD.

Cum

ulat

ive

% (M

ean+

SE

) tot

al a

nd to

spov

irus

infe

sted

tom

ato

plan

t

0

2 0

4 0

6 0

8 0

1 0 0

T o t a l - V i r u s T o s p o V i r u s

a

b

c

c

aa

b

d( A )

T r e a t m e n t

B ( N + P ) N B - N + B - P B - N + N B - P N B ( N + P )

Cum

ulat

ive

% (M

ean+

SE)

tota

l and

tosp

oviru

s in

fest

ed to

mat

o pl

ant

0

2 0

4 0

6 0

8 0

1 0 0

aa

b

c

a a

b

c( B )


5.4. Discussion These studies are probably the first of its kind from protected cultivation in SE

Asia, investigating the entry of three plants sucking insect pest, WF, thrips and

aphids and related virus spread in tropical greenhouses covered with UV�

blocking material compared to those with non-blocking properties. Whitefly Immigration. The UV deficient environment in all three experiments

reduced entry and attraction of WF towards or inside the greenhouses.

Strongest differences were observed between greenhouses completely covered

by UV blocking material (B (N+P) type GH) compared to those made from UV

transmitting plastics and nets (NB (N+P) type GH). This entry trend was true

irrespective of the length of the time GH gates were opened for ventilation but

fewer WF immigrated and were trapped (YST) under the B (N+P) GH type,

when gates were opened for 4-5 hrs per day only in the morning compared to

experiments with parallel gates kept open long time for full ventilation. When the

attraction of WF towards the structures was monitored by outside on the walls

positioned traps much lower numbers were trapped around the UV blocking

houses compared to the non-blocking ones. The results clearly indicate very

sensitive reaction of WF adults to the presence of the total amount of UV inside

a GH irrespective of the individual blocking properties of either nets or plastic

used in the experiment.

The reduced immigration and attraction of WF inside UV deficient GH or

towards sidewalls of UV-blocking material are in agreement with previously

reported studies of Antignus et al. (1996, 1998, 2001) and Costa and Robb

(1999). Similarly in recent studies Gonzalez (2004) working with B. tabaci and

Mutwiwa et al. (2005) working with T. vaporariorum reported significantly lower

numbers of WF trapped under UV low GH over GH with high UV. Most of these

investigations showed a highly significant reduction in WF flight intensity and

immigration into UV-poor tunnels/net house/greenhouse. Most of these studies

used UV-blocking plastics, whereas Antignus et al. (1998, 2001) covered

tunnels completely with UV-blocking nets and achieved a long-term protection

of plants inside from B. argentifolii. Moreover, when we measured the incoming

radiation inside these structures (see fig. 2), we found that plastic roofs of our

small greenhouses blocked more efficiently the UV- radiation than nets at the

sidewalls. Wherever we used the UV-blocking plastic roofs, internal UV-


radiation was lowest. The immigrating WF showed an UV-intensity dependent

behavior. For instance, during experiment 1, on a typical sunny day at 12.00 h,

inside GH types NB (N+P) we recorded UV intensity of 12.47 wm-2 followed by

8.10 wm-2 in the B-N+NB-P, 1.45 wm-2 under NB-N+B-P and 0.55 wm-2 under B

(N+P) type GH (see figure 5.2). These levels of UV radiation decreased to half

in respective GH types during cloudy days but the differences in attraction of

WF persisted further on between the GH types. This indicates that not the

absolute UV amount available triggers WF selection behavior but the relative

difference between two light environments. Similar findings on reduced

movement, dispersal and colonization under UV deficient conditions of another

WF species in greenhouses, T. vaporariorum are recently reported by Doukas

(2002) and Mutwiwa et al. (2005).

Similar to the trends of trapping with YST, significantly higher number of WF per

leaf was recorded under the NB (N+P) GH either with short opening (4-5 hrs) or

when gates kept open permanently. This indicates that YST trapping is giving a

clear picture of WF settling and population development on the plants. Reduced

population built up of WF under UV deficient environment is in line with

previously published reports (e.g. Antignus et al. 1996, 1998, Summers et al.

2004). Our results seem to be only in disagreement with those of Costa et al.

(2002), who found insignificant differences in WF numbers on plants in

greenhouses made of UV-absorbing compared to UV-transmitting plastics.

These contradictions could be due to the fact that in our experiment, only the

gates were opened but not the sidewalls. However, we also found more WF,

thrips and aphids on the tomato plants near the gates under B (N+P) GH

compared to the centre of the GH. Even the virus infected plants in this type of

GH are always recorded near the opening gates. Similar observations were

made by Mutwiwa et al. (2005).

Clearly, the UV reduced GH environment achieved through the combination of

the UV-blocking plastics and nets were able to dramatically reduce the number

of WF movement to the wall of greenhouses, entering inside and numbers

settling on plants. The exact mechanism of this effect is still unknown, but it is

presumed that reduced immigration and dispersal levels result from interference

with visual cues which trigger the selection of environment for flight activity and

orientation to and selection of plants for settlement (Antignus 1996, Antignus et


al. 1998, 2000, Mutwiwa et al. 2005). That WF might be able to react to UV is

shown by Mellor et al. (1997), who described UV sensitive photoreceptors for

the greenhouse WF, T. vaporariorum. No such detailed information is available

for B. tabaci.

Aphid Immigration. Winged aphids followed similar trends considering the

different GH types as previously discussed for WF independent whether they

were trapped with YST or accounted on the plants These results are in line with

earlier published reports by Antignus et al. (1996, 1998) or Chyzik et al. (2003)

who reported trapping 50 times more alate aphids under normal condition over

UV-blocked conditions. Recent studies (see Kirchner et al. 2005) show that

aphids have photoreceptors in their compound eyes sensitive to light in the UVA

range of the light spectrum; however detailed studies about the importance of

light reception in the UV range for aphid behavior are still missing. The

increased number of aphid nymphs inside the NB (N+P) GH could well be due

to its increased propagation time over B (N+P) GH types. Propagation time of

aphid (Myzus persicae) was reported to 1.5 � 2 times longer under regular film

compared to UV-absorbing films and UV exposed aphids give more birth to new

progeny (Chyzik et al. 2003).

Thrips immigration and leaf damage. The thrips, Ceratothripoides claratris

gave a very sensitive response to the changes in UV-environment and

irrespective of ventilation period (partial or complete), preferred to enter inside

UV-rich environment in a concentration-dependent manner. Thrips followed the

same trend as WF and aphids in their attraction towards the various

greenhouses. Higher numbers of thrips immigrating into NB (N+P) type GH

resulted in higher number of damaged leaves per plant. Since no previous

investigations with C. claratris are reported, results were compared with other

thrips species. Our results are consistent with findings on WFT, F. occidentalis

(Pergrande) from Israel, where significant reduction of the thrips were found

under UV-absorbing plastic tunnels (Antignus et al. 1996). Similarly, in a choice

study Costa et al. (1999) captured 90-98% of released F. occidentalis

(Pergrande) under tunnels rich in UV over tunnels covered with UV-absorbing

plastics. On the other hand Antignus et al. (1998), could not significantly reduce

the immigration of F. occidentalis with tunnels made of 50-mesh UV �blocking

Bionets®. The discrepancy to our results could be explained by the different set-


ups since we used a combination of UV-blocking plastics and nets with much

higher UV-blocking capacity compared to Bionet only. Similar to aphids the

ability of thrips to receive light in the UV range spectrum is well documented

(Matteson et al. 1992) even a differentiation between UV-A and UB-B. Mazza et

al. (1996, 2002) showed that the thrips Caliothrips phaseoli avoids UV-B but is

attracted by UV-A and Vernon and Gillespie (1990) reported that high UV

reflectance environment repels thrips. The selective sensitivity of thrips to

different UV ranges becomes obvious when we compare our results with

reports on the use of UV-reflective mulches against thrips. Some reports are

available for tomato and capsicum crops, where use of UV-reflective mulch

caused significant reduction in WFT, F. occidentalis (Pergrande) population

(Scott et al. 1989, Greenough et al. 1990, Brown and Brown 1992, Kring and

Schuster 1992, Vos et al. 1995, Costa et al. 2002, Stavisky et al. 2002,

Gonzalez 2004). Similarly, other species of thrips were repelled using plastic

reflective mulches in outdoor ornamentals and vegetable crops (Csizinski et al.

1995, Terry 1997). It could be speculated that the specific reflection pattern of

UV is important in determining whether thrips is attracted to a host or repelled

and that relative high amounts of reflected UV-B can overrule the attractive

properties of UV-A. This interesting relation should be studied more in detail.

Plant Virus. Thrips, C. claratris is recently reported to be a serious pest of

protected cultivation of tomato in the greater Bangkok area and vector of

tospovirus, CaCV (isolate AIT) (Premachandra et al. 2005). Number of plants

showing virus symptoms, which was later confirmed through ELISA test,

followed the trends of the immigrating thrips and WF, which was recorded least

under the B (N+P) type GH over NB (N+P) type GH. B (N+P) GH reduced and

delayed the virus infection in all experiments. Majority of recorded virus was the

tospovirus as evident through the thrips as most occurring species. However,

no further attempts were made to isolate other viruses but it could be

speculated that Tomato Yellow Leaf Curl Virus (TYLCV) virus was one more

virus, since symptoms were fitting. Furthermore it is transmitted by WF, and it is

very frequently observed in field crops in the study area. In Israel, the spread of

TYLCV were significantly reduced using UV-absorbing nets (Antignus et al.,

1996, 1998, Gonzalez 2004) and the incidence of cucurbit yellow stunting

disorder virus in melons were reported to be 70% less under UV-absorbing films


and the same film appeared to be effective against aphid-borne Zucchini yellow

mosaic virus (Antignus 2000). Same way as discussed above is should be

mentioned that UV-reflective mulches can significantly reduce the incidence of

thrips vectored viruses as shown with Tomato Spotted Wilt Virus, which was

vectored by Frankliniella spp (Stavisky et al. 2002). Moreover the use of

aluminum or silver plastics mulches delayed the infection and spread of TYLCV

in Jordan (Suwwan et al. 1988) and effectively protected tomato against tomato

mottle virus in Florida (Csizinski et al. 1995).

Conclusions

In conclusion, our result show that the greenhouses made from a combination

of the UV-blocking nets as side walls and roof from UV- blocking plastics are

able to significantly limit immigration of WF, aphids and thrips into such

structure and consequently tomato plants grown under such GH had fewer pest

populations resulting into fewer leaf damage as well as reduced virus infections.

Being in the tropics, the major amount of light filters though the roof, hence UV-

blocking plastic on roof can efficiently reduce the incoming UV. Nets on

sidewalls however are a prerequisite for low cost non-cooled greenhouses to

achieve sufficient ventilation. UV-blocking nets although not so efficient as films

in the blocking abilities can ideally supplement the UV blocking film roof

material. Reducing immigration of the pests in greenhouse leads to a lower

initial pest population density, which is a key factor for successful and effective

control in general (Xu et al. 1984). Other potential benefits from the reduced

UV-environment achieved through the use of UV-blocking net and plastics may

include improved performance of entomopathogenic fungi (Costa et al. 2001),

and baculoviruses (Goulson et al. 2003), improved management of some fungal

pathogens (Reuveni and Raviv 1992, Elad 1997), reduced UV related

degradation of botanicals like neem (Barnaby et al. 1989, Stokes and Redfern

1982, Johnson et al. 2003, Barrek et al. 2004), and overall improvements in the

microclimate, but that has to be confirmed in further studies.

Final Discussion 99

6 Final Discussion

Main details of our studies are discussed in the chapters above; here we will

give a final short and comprehensive review and valuation of the achieved

results and their broader importance for integrated pest management (IPM) of

WF under protected cultivation in the humid tropics.

Tomato production in Thailand is seriously constrained by WF (Bemisia tabaci)

and other insect-pests like thrips, leafminers, fruit worm (Helicoverpa sp.), etc.

and among them Bemisia vectored TYLCV is major production constraint

causing up to 100% losses (Attathom et al. 1990, Sawangjit et al. 2005). Over

600 different plant species have been recorded as host of WF (Mound & Halsey

1978, Greathead 1986, Cock 1986, Secker et al. 1998) and it can easily adapt

to a new host and environment. It feeds on a wide variety of vegetable crops

such as tomato, pepper, beans, eggplant and cucumber both under field and

protected cultivation environment. The present focus on chemical management

is seriously limited. Furthermore, faster resistance development leads to

ineffective management of WF either with old conventional insecticides, or with

first or second generation of nicotinoids [(Schuster (2000a and 2000b),

Schuster and Polston (1997a, 1997b, 1998) Palumbo and Coates 1996)] or

even with growth regulators (Horowitz et al. 1999 a & b, Denholm et al. 1998,

Ellsworth et al. 1996, Dennehy et al. 1996).

Therefore, alternative control strategies for WF focusing on botanicals like neem

are needed. A detail comparison of application methods (topical vs. systemic) at

different dose-rates and learning the sensitivity of different WF developmental

stages are of crucial importance (chapter 2) for sustainable tomato production

under dynamic climatic condition of the humid tropics. Any attempt to combine

successful bio-control agents like Eretmocerus and Encarisa with a botanical

like neem would need information on the persistency (chapter 3) to develop the

integrated control strategies. Similarly, so called novel bio-pesticides of

microbial origin like abamectin and spinosad were compared in laboratory and

in GH (chapter 4) with neem to provide detailed comparison and persistency to

further dwell on the idea of the developing integrated control for WF. Moreover,

reducing the infection pressure of WF by retarding the immigration into the GH

environment by mechanical and optical barriers could contribute to sustainable

6

Final Discussion 100

management. Consequently combinations of UV-blocking nets and plastics

(Chapter 5) were tested.

Our findings related to neem and its various application methods (seed soaking,

foliar and systemic) revealed that neem could provide excellent control of

Bemisia in a concentration dependent manner (chapter 2). It first acts to repel

the settling of adults on the treated plants resulting into reduction of the overall

egg load on the plant; moreover, it caused reduction in egg hatching and high

immature mortality. Similarly, we found that with different application methods, a

different load of tomato leaves with active neem ingredients was achieved,

where major feeding, egg laying and immatures development takes place.

Foliar application was found a very efficient way to apply neem to the leaves,

where it causes almost 100% immatures mortality followed by the systemic

application and seed soaking. Most striking was the high efficacy of the

systemic use of neem opening new venues to affect a leaf sucking herbivore

pest without contaminating the crop canopy and wider environment. Therefore,

an integrated strategy of using tomato seedlings grown out with neem seed

soaking followed by a combination of foliar and soil application of neem is

suggested as a first convenient tool to achieve an efficient and sustainable

control of B. tabaci on tomatoes grown under tropical net houses.

When we studied the persistency of the neem applied by soil drenching or foliar

spraying under GH and lab conditions (chapter 3) variable rates of degradation

were evident measured by dynamic changes in adult colonization, and

subsequent egg deposition, egg hatching and immature mortality. The neem

ingredients applied to the plant roots were translocated into the plant vessel

system and are there protected from abiotic degradation factors and less

vulnerable to degradation compared to the neem applied on the foliage.

The reduction in the bio-efficacy of leaf sprayed neem was clearly related to the

UV and temperature as dissipation rate was rapid under GH compared to lab

conditions. Fresh foliar residues provided excellent control of Bemisia for first

few days but quickly degraded to a point where no bio-efficacy was noted. In

contrast, the systemically translocated neem steadily provided excellent control

over a longer period of time. Thus, making the soil application a safer way to

preserve the bio- efficacy of applied neem compared to the foliar applied neem.

However, soil drenching requires higher quantity of neem compared to the foliar


application to achieve similar level of WF control, thus, making it economically

costlier option for the growers. In addition, use of neem as a systemic pesticide

for crops grown under protected cultivation, has advantages, i.e. where plants

can be grown in pots or on artificial substrates; and where the infection pressure

can be reduced by the use of mechanical barriers such as nets. Moreover, soil

drenching of neem would least interfere with the foliage dwelling parasitoids

because of lack of any direct contact, thus, would open the door for synergistic

use of the biopesticide (�fast task force�) and parasitoids or predators (�long

term sustainable control�).

Neem has already gained public acceptance in developed countries for use on

food crops (Isman1994) because of reduced human toxicity, fast and complete

degradation in the environment, low risk for resistance and sometimes selective

properties concerning non-target organism (Feng and Isman 1995, Immaraju

1998, Walter 1999). A possible drawback of using neem is the cost of $1,500

US per ton of neem oil (Stone 1992) and the further cost of formulation. In

contrast, neem being a native of India and part of Asia (developing world) is

widely grown and a range of neem derived pesticides products (neem oil, kernel

powder, oil cake, dried leaves etc.) are traditionally used and are available.

Similarly being the producing countries of neem, costs are relatively very small

e.g. in India cost of neem oil as low as Rs.20/kg10 (Mruthyunjaya and Jha 1996).

Thus, more then the pricing of neem products, quality and consistency of the

marketed neem products would determine its wider use and adoptability by

growers for vegetable production including tomatoes.

Our work with neem, spinosad and abamectin (chapter 4) revealed that B.

tabaci are highly susceptible to neem, spinosad and abamectin. However, the

susceptibility varies with WF growth stage and time span between application

and infestation as well as the presence and absence of sunlight. The adult

colonization was deterred by the neem and abamectin and consequently

reduced egg deposition was observed. However, no such deterrency of adult

and consequent reduced rate of oviposition was observed for spinosad.

Abamectin treatment seriously affected the hatching of the WF eggs but only a

concentration dependent response was observed for the neem and spinosad.

Neem, spinosad and abamectin caused heavy mortality of all three larval stages

10 45 Indian Rupees (Rs.) = 1 US$ (2005 exchange rate).


of B. tabaci, where the first instar larvae was found to be most susceptible

compared to other two larval stages. The abamectin treated larvae died faster

(24 h) compared to 6-9 days in case of neem and spinosad. In terms of

persistency, abamectin gave most persistent activity either under lab or in GH

condition, whereas, there was considerable loss of efficacy of spinosad and

neem was observed under GH condition, which was better under lab condition.

However, neem products can help to control the serious pest B. tabaci in a

more safe and sustainable manner particularly if only short term effects are

necessary since remigration of the pest, e.g. in GH, is low. Thus, we foresee

that WF management in tropically adapted GHs, if necessary for longer periods

under heavy infestation pressure can not be achieved with this botanical alone.

It requires a combination of neem and other safe products like spinosad or even

abamectin, if necessity of product rotation to avoid resistant selection is

considered. Particularly the highly efficient spinosad seems to be under risk of

fast selection of resistant biotypes if used frequently (Zhao et al. 2002).

Regarding combined IPM strategies with a combination of pesticides and

natural enemies, our results provide a promising future basis for integrating the

WF parasitoid, Eretmocerus nr. warrae11 (Hymenoptera: Aphelenidae)

commonly present in and around the GH complex of AIT, Bangkok with a

botanical pesticide like neem. However, several follow up studies would be

important to increase our present understanding of such a combined strategy,

like fate of applied neem inside plants; effect of neem application methods at

different dose-rates on the overall fitness, development stages, behavior of the

parasitoids, its effect on the second generation parasitoids. On another front,

the knowledge on effects of brake-downs and analogs of azadirachtin on the

Bemisia etc. would also be needed for successful and sustainable management

of WF. Moreover the possible combination of biopesticides with release of

natural enemies should be studied more in detail. That requires reliable data

about possible side effects under practical growing conditions.

Vegetable crops like tomatoes grown under protected cultivation (net house,

tunnels etc.) in humid tropics are vulnerable to abiotic stress (temperature,

humidity, air flow etc.) (Ajwang et al. 2002) and biotic stresses represented by

11Identified by: Dr. Stefan Schmidt, Hymenoptera Section, Zoologische Staatssammlung Muenchen, Muenchhausenstr. 21, 81247 Munich, Germany


insects (WF, thrips, aphid) and plant virus diseases vectored by these insects

like Tomato Yellow Leaf Curl (TYLCV) and tospovirus ((Tanapas et al. 1983,

Thongrit et al.1986, Attathom et al. 1990, Ketelaar and Kumar, 2002,

Premachandra 2004). As a novel attempt, it was planned to combine UV-

blocking plastics as roof and UV-blocking nets as side walls to improve

microclimate and reduce immigration of insects. A lower initial pest population

density is a key factor for successful and effective control in general (Xu et al.

1984). The results (Chapter 5) revealed that GH made from a combination of

UV-blocking nets as side walls and roofs with UV- blocking plastics are able to

deter the immigrating WF, aphids and thrips. Consequently tomato plants grown

under such GH`s had fewer leaf damage and we expect furthermore reduced

virus infection including those of tosposvirus. Other potential benefits from the

reduced UV-environment achieved through the use of UV-blocking net and

plastics may include improved performance of entomopathogenic fungi (Costa

et al. 2001), and baculoviruses (Goulsom et al. 2003), improved management of

some fungal pathogens (Reuveni and Raviv 1992, 1997, Elad 1997), reduced

UV related degradation of botanicals like neem (Barnaby et al. 1989, Stokes

and Redfern 1982, Johnson et al. 2003, Barrek et al. 2004), and overall

improvements in the microclimate leading to healthier production of crops like

tomatoes. Thus, such GHs present itself as a viable option over all plastic made

GHs in the humid tropics. However, additional questions like insects entry

though the nets and their dispersal rates, effect of reduced UV-lights on the

reproduction behavior of the WF and thrips etc. needs to be analyzed and will

be subject of the further investigations.

In conclusion, the results presented in this work show that WF could be

efficiently managed by the botanicals like neem and other so called bio-rational

like spinosad and abamectin, if used properly. Moreover, under high UV

environment of the humid tropics, selection of right concentration is essential to

achieve sustainable level of management. Furthermore, under protected

cultivation, physical control by using UV-blocking plastic and nets hold lot of

promise, where several other non-chemical management options could be

integrated to further reduce the WF damage levels. Data presented here can

provide sound baseline information for the development of the IPM of the WF

using alternatives to chemicals.

Refrences cited 104

References cited

Abou-Fakhr Hammad, E. M., N. M. Nemer, Z. K. Hawi, and L. T. Hanna. 2000. Responses of the sweetpotato whitefly, Bemisia tabaci to the

Chinaberry tree (Melia Azedarach L.) and its extracts. Annals of

Applied Biology. 137: 79-88.

Abou-Fakhr Hammad, E. M., H. Zournajian, and S. Talhouk. 2001. Efficacy

of extracts of Melia azedarach L. callus, leaves and fruits against adults

of sweetpotato whitefly Bemisia tabaci (Hom., Aleyrodidae). Journal of

Applied Entomology. 125: 483-488.

Ajwang, P., H. J. Tantau., and C. V. Zabeltitz. 2002. Insect screens for

integrated production and protection in greenhouses: a review of the

physical and technical basics. Gartenbauwissenschaft. 67: 45-49.

Akey, D.H., and T. J. Henneberry. 1999. Control of silverleaf whitefly with the

neem product azadirachtin as bollwhip in upland cotton in Arizona.

Proceedings of Beltwide Cotton Conference. 2: 914-918.

Anonymous, 2001. Crop Protection Compendium, Global Module, 3RD edn.

CAB International CD-Rom Database.

Anonymous, 2002. Integrated Pest management (IPM) and green farming in

rural poverty alleviation in Thailand.

http://www.unescap.org/rural/doc/ipm2002/ch12.pdf. Accessed on

17.09.2005.

Anonymous, 2005a. Encyclopedia: Tomato, Spanish distribution.

http://www.nationmaster.com/encyclopedia/Tomato.Assessed on

03.09.2005.

Anonymous, 2005b. Thailand information. Agriculture SUNSITE Thailand.

http://sunsite.au.ac.th/thailand/agriculture/Crop.html. Accessed on

15.09.2005.

Antignus, Y. 2000. Manipulation of wavelength dependent behaviour of

insects: an IPM tool to impede insects and restrict epidemics of insect

borne viruses. Advances in Virus Research. 71: 213-220.

Antignus, Y., D. Nestel, S. Cohen, and M. Lapidot. 2001. Ultraviolet deficient

greenhouse environment affects whitefly attraction and fight behaviour.

Environmental Entomology. 30: 394-399.

7

Refrences cited 105

Antignus, Y., M. Lapidot, D. Hadar, M. Messika, and C. Cohen. 1998. Ultraviolet absorbing screens serve as optical barriers to protect

greenhouse crops from virus diseases and insect pests. Journal of

Economic Entomology. 9: 1401-1405.

Antignus, Y., M. Lapidot, N. Mor, R. Ben-Joseph, and S. Cohen. 1996a. Ultra violet absorbing plastic sheets protect crops from insect pests and

virus diseases vectored by insects. Environmental Entomology. 25:

919-924.

Antignus, Y., S. Cohen, N. Mor, Y. Messika, and M. Lapidot. 1996b.The

effects of UV blocking greenhouse covers on insects and insect-borne

virus diseases. Plasticulture. 11: 15-20.

Ascher, K. R. S., J. Meisner, and M. Klein. 2000. Neem-based biopesticides

against the western flower thrips and the onion thrips. Phytoparasitica.

28: 87-90.

Ashekanzi, Y. 1996. Improving the properties of polyethylene films for

agricultural uses. Acta Horticulturae. 434: 205-212.

Attathom, S., P. Chiemsombat, T. Sutabutra, and R. Pongpanitanond. 1990. Characterization of nucleic acid of a tomato yellow leaf curl

virus. Kasetsart Journal (Natural Science). 24:1-5.

Barnby, M. A., R. B. Yamasaki., and J. A. Kloske. 1989. Biological activity of

azadirachtin, three derivatives, and other ultraviolet radiation

degradation products against tobacco budworm (Lepidoptera:

Noctuidae) larvae. Journal of Economic Entomology. 82: 58-63.

Barrek, S., O. Paisse, and G.-L. Marie-Florence. 2004. Analysis of neem oils

by LC-MS and degradation kinetics of azadirachtin-A in a controlled

environment. Analytical and Bioanalytical Chemistry. 378: 753-763.

Bedford, I., R. W. Briddon, J. K. Brown, R. C. Rosell, and P. G. Markham. 1994. Geminivirus transmission and biological characterization of

Bemisia tabaci (Gennadius) biotypes from different geographic regions.

Annals of Applied Biology. 125: 311�325.

Refrences cited 106

Bedford, I. D., R. W. Briddon, P.G. Markham, J. K. Brown, and R. C. Rosell. 1992. Bemisia tabaci-biotype characterization and the threat of this

whitefly species to agriculture. In: Brighton Crop Protection Conference-

Pests and Diseases. British Crop Protection Council, Farnham, UK, pp.

1235�1240.

Berlinger, M. J. 1992. Pests of processing tomatoes in Israel and suggested

IPM model. Acta Horticulturae. 301:185-192.

Berlinger, M. J., R. Dahan, and S. Mordechi. 1988. Integrated pest

management of originally grown greenhouse tomatoes in Israel. Applied

Agricultural Research. 5: 233-238.

Bharathan, N., W. R. Graves, K.R. Narayanan, D. J. Schuster, H. H. Bryan and R.T. McMillan, Jr. 1990. Association of double stranded RNA with

whitefly-mediated silvering in squash. Plant Pathology. 39: 530-538.

Bird, J., 1957. A whitefly transmitted mosaic of Jatropha gossypifolia. Univ.

Puerto Rico, Agriculture Experiment Station. 22: 35.

Bird, J., and K. Marmorosch. 1978. Viruses and virus diseases associated

with whiteflies. Advances in Virus Research. 22: 55�110.

Boek, L. D., C. Hang, T. E. Eaton, O. W. Godfrey, K. H. Michel, W. M. Nakatsukasa, and R. C. Yao. 1994. Process for producing A 83543

compounds. US Patent No. 5,362,634. Assigned to DowElanco.

Bret, B. L., L. L. Larson, J. R. Schoonover, T. C. Sparks, and G. D. Thompson. 1997. Biological properties of the Spinosad. Down to Earth.

52: 6-13.

Brown, J. E., J. M. Dangler, F. M. Woods, M. C. Henshaw, W. A. Griffy, and M. W. West. 1993. Delay in mosaic virus onset and aphid vector

reduction in summer squash grown on reflective mulches. HortScience.

28: 895-896.

Brown, J. K., D. R. Frohlich, and R. C. Rosell. 1995. The sweetpotato or

silverleaf whiteflies; biotypes of Bemisia tabaci or a species complex?

Annual Review of Entomology. 40.

Brown, J. K., S. Coats, J. D. Bedford, P. G. Markham, J. Bird. 1992. Biotypic

characterization of Bemisia tabaci populations based on esterase

profiles, DNA fingerprinting, virus transmission, and bioassay to key host

plant species. Phytopathology. 82: 1104.

Refrences cited 107

Brown, J.K., and J. Bird.1992. Whitefly-transmitted geminiviruses and

associated disorders in the Americas and the Caribbean Basin. Plant

Disease. 76: 220�225.

Brown, J.K., D. R. Frohlich, R. C. Rossell. 1995. The sweet potato or

silverleaf whiteflies: biotypes of Bemisia tabaci or a species complex?

Annual Review of Entomology. 40: 511�534.

Brown, S. L., and J. E. Brown. 1992. Effect of plastic mulch colour and

insecticides on thrips populations and damage to tomato.

HortTechnology. 2: 208-210.

Burban, C., L. D. C. Fishpool, C. Fauquet, D. Fargette, and J. C. Thovenel. 1992. Host-associated biotypes within west African populations of the

whitefly Bemisia tabaci (Gennadius.), (Hom., Aleyrodidae). Journal of

Applied Entomology. 113: 416�423.

Butler Jr., G. D., J. K. Brown., and T. J. Henneberry. 1986. Effect of cotton

seedling infection by cotton-leaf crumple virus on subsequent growth

and yield. Journal of Economic Entomology. 79: 208-211.

Butler Jr., G. D., T.J. Henneberry, and W. D. Hutchinson. 1986. Biology,

sampling and population dynamics of Bemisia tabaci, In: G.E. Russell

[Ed.], Agricultural Zoology Reviews. Intercept, UK, pp. 167�195.

Butler Jr., G.D., and T. J. Henneberry. 1986. Bemisia tabaci (Gennadius), a

pest of cotton in the southwestern United States. US Dept. Agric.,

Agriculture Research Service Technical Bulletin. 1701: 19.

Buxton, J. H., and O. C. McDonald. 1994. Chemical control of the south

American leaf miner, Liriomyza huidobrensis. Brighton Crop Protection

Conference, Pest and Diseases. British Crop Protection Council, BCPC

Publications, Bracknell, UK, Brighton, UK, 21-24 November, 1994, pp.

731-736.

Byrne, D. N., T. S. Bellow, and M. P. Parella. 1990. Whiteflies in agricultural

systems. In: D. Gerling [ed.], Whiteflies: Their Bionomics, Pest Status

and Management. Intercept, Andover, pp. 227-261.

Byrne, F. J., S. Castle, N. Prabhaker, and N. C. Toscano. 2003. Biochemical

study of resistance to imidacloprid in B biotype Bemisia tabaci from

Guatemala. Pest Management Science. 59: 347-352.

Refrences cited 108

Caboni, P., M. Cabras, A. Angioni, M. Russo, and P. Cabras. 2002.

Persistence of azadirachtin residues on olives after field treatment.

Journal of Agricultural and Food Chemistry. 50: 3491-4.

Cahill, M., and I. Denholm. 1999. Managing resistance in the chloronicotinyl

insecticides- rhetoric or reality. In: I. Yamamoto, J. E. Casdia, [eds.],

Nicotinoid Insecticides and the Nicotinic Acetylcholine Receptor.

Springer, Tokyo, pp. 253�270.

Cahill, M., F. J. Byrne, K. Gorman, I. Denholm, and. A. L. Devonshire. 1995. Pyrethroid and organophosphate resistance in the tobacco whitefly

Bemisia tabaci (Homoptera: Aleyrodidae). Bulletin of Entomological

Research. 85:181�187.

Cahill, M., I. Denholm, F. J. Byrne, and A. L. Devonshire. 1996. Insecticide

resistance in Bemisia tabaci- current status and implications for

management. In: Brighton Crop Protection Conference: Pests and

Diseases. British Crop Protection Council, Brighton, UK, pp. 75�80.

Charungphan, S. 2002. Population Dynamics and Biological Control of

Whitefly, Bemisia tabaci Gennadius (Homoptera; Aleyrodidae), on

Tomato under Protected Cultivation in Thailand. Graduate School.

Kasetsart University, Thailand. M. Sc. Thesis. 44 p.

Chyzik, R., S. Dobrinin, and Y. Antignus. 2003. Effect of a UV-Deficient

Environment on the Biology and Flight Activity of Myzus persicae and Its

Hymenopterous Parasite Aphidius matricarie. Phytoparasitica 31: 467-

477.

Cleveland, C. B., M. A. Mayes, and S. A. Cryer. 2001. An ecological risk

assessment for spinosad use on cotton. Pest Management Science. 58:

70-84.

Cock, M. J. N., 1986. Bemisia tabaci - A literature survey on the cotton whitely

with an annotated bibliography. FAO/CAB International Institute of

Biological Control. Ascot, UK. 21 pp.

Cohen, S., and V. Melamed-Madjar. 1978. Prevention by soil mulching of

spread of tomato yellow leaf curl virus transmitted by Bemisia tabaci

(Gennadius) (Hemiptera: Aleyrodidae) in Israel. Bulletin of Entomological

Research. 68: 465-470.

Refrences cited 109

Costa, A.S., L. M. Russell. 1975. Failure of Bemisia tabaci to breed on

cassava plants in Brazil (Homoptera: Aleyrodidae). Ciencia e Cultura

(Sao Paulo). 27: 388�390.

Costa, H. S., and K. L. Robb. 1999. Effects of Ultraviolet-Absorbing

Greenhouse Plastic Films on Flight Behaviour of Bemisia argentifolii

(Homoptera: Aleyrodidae) and Frankliniella occidentalis (Thysanoptera:

Thripidae). Journal of Economic Entomology. 92: 557-562.

Costa, H. S., K. L. Robb, and C. A. Wilen. 2001. Increased persistence of

Beauveria bassiana spore viability under high ultraviolet-blocking

greenhouse plastic. Hortscience. 36: 1082-1084.

Costa, H., K. L. Robb, and C. A. Wilen. 2002. Field trials measuring the effect

of ultraviolet absorbing greenhouse plastic films on insect populations.

Journal of Economic Entomology. 95: 113-120.

Costa, H.S., J. K. Brown. 1990. Variability in biological characteristic isozyme

patterns and virus transmission among populations of Bemisia tabaci

Genn. in Arizona. Phytopathology 80: 888.

Costa, H.S., J. K. Brown, and D. N. Byrne. 1991. Life history traits of the

whitefly, Bemisia tabaci (Homoptera: Aleyrodidae) on six virus infected or

healthy plant species. Environmental Entomology. 20:1102�1107.

Costa, H.S., J. K. Brown. 1991. Variation in biological characteristics and

esterase patterns among populations of Bemisia tabaci, and the

association of one population with silverleaf symptom induction.

Entomologia Experimentalis et Applicata. 61:211�219.

Coudriet, D. L., N. Prabhaker., and D. E. Meyerdirk. 1985. Sweetpotato

Whitefly (Homoptera: Aleyrodidae): Effects of Neem-seed Extract on

Oviposition and Immature Stages. Environmental Entomology. 14: 776-

779.

Cowles, R. S. 2000. Inert formulation ingredients with activity: toxicity of

trisiloxane surfactant solutions to two spotted mites. Journal of Economic

Entomology. 93: 180-188.

Csizinski, A. A., D. J. Schuster, and J. B. Kring. 1995. Colour mulches

influence yield and insect pest populations in tomatoes. Journal of the

American Society for Horticultural Science. 20: 778�784.

Refrences cited 110

De Barro, J. P. 1995. Bemisia tabaci biotype B: A review of its biology,

distribution and control, Second Ed. Division of Entomology. Technical

Paper No. 36. CSIRO, Canberra, Australia.

De Jager, C. M., and R. P. T. Butot. 1993. Chrysanthemum resistance to two

types of thrips (Frankliniella occidentalis Pergande) feeding damage.

Proceedings of Experimental and Applied Entomology. Netherlands

Entomological Society. 4:27-32.

Deang, R. T. 1969. An annotated list of insect pests of vegetables in the

Philippines. Philippine Entomologist. 1: 313-333.

Denholm, I., M. Cahill, F. J. Byrne, and A. L. Devonshire. 1996. Progress

with documenting and combating insecticide resistance in Bemisia. In:

D. Gerling and R. T. Mayer [eds.], Bemisia: 1995 taxonomy, biology,

damage, control and management. Intercept, Andover, United

Kingdom, pp. 577-603.

Denholm, I., M. Cahill, T. J. Dennehy, and A. R. Horowitz. 1998. Challenges

with managing insecticide resistance in agricultural pests, exemplified

by the whitefly Bemisia tabaci. Philosophical Transactions of the Royal

Society of London, Series B. 353:1757�1767.

Dennehy, T. J., P. C. Ellsworth, and R. L. Nichols. 1996. The 1996 whitefly

resistance management program for Arizona cotton. University of

Arizona, Cooperative Extension, IPM Series No. 8, 16pp.

Dittrich, V., G. H. Ernat O. Ruesh, and S. Uk. 1990a. Resistance mechanism

in sweetpotato whitefly (Homoptera: Aleyrodidae) population from

Sudan, Turkey, Guatemala and Nicaragua. Journal of Economic

Entomology. 83: 1665-1670.

Dittrich, V., S. Uk, and G.H. Ernst. 1990b. Chemical control and insecticide

resistance of whiteflies. In: Gerling, D. (Ed.), Whiteflies: their

Bionomics, Pest Status and Management. Intercept, Andover, UK, pp.

263�286.

Doukas, D. 2002. Impact of spectral cladding materials on the behaviour of

glasshouse whitefly Trialeurodes vaporariorum and Encarsia formosa,

its hymenopteran parasitoid, School of Plant Sciences. M.Sc.

dissertation, The University of Reading, London, United Kingdom.

Refrences cited 111

Dow, Agrosciences. 1997. Spinosad Technical Bulletin. Dow Agrosciences:

15 pp.

Duffus, J. E. 1987. Whitefly transmission of plant viruses. Current Topics in

Vector Research. 4: 73-91.

Elad, Y. 1997. Effect of solar light on the production of conidia by field isolates

of Botrytis cinerea and on several diseases of greenhouse grown

vegetables. Crop Protection. 16: 635-642.

Elbert, A., and R. Nauen. 2000. Resistance of Bemisia tabaci (Homoptera:

Aleyrodidae) to insecticides in southern Spain with special reference to

neonicotinoids. Pest Management Science. 56: 60-64.

Ellsworth, P.C., T. J. Dennehy, and R. L. Nichols. 1996. Whitefly

management in Arizona cotton 1996, IPM Series No. 3. The University

of Arizona, Cooperative Extension, Publication #196004. Tucson, AZ, 2

pp. http://ag.arizona.edu/crops/ cotton/insects/wf/ cibroch.html.

Accessed on 15.09.2005.

Espinosa, P. J., P. Bielza, J. Contreras, and A. Lacasa. 2002. Field and

laboratory selection of Frankliniella occidentalis (Pergande) for

resistance to insecticides. Pest Management Science 58: 920-927. FAOSTAT data, 2005. last updated 14 July 2005.

http://faostat.fao.org/faostat/collections?version=ext&hasbulk=0&subse

t=agriculture. Assessed on 03.09.2005. Feldhege, M., and H. Schmutterer. 1993. Investigations on side effects of

Margosan-O on Encarsia formosa Gah. (Hym., Aphelenidae),

parasitoid of the greenhouse whitefly Trialeurodes vaporariourum

Westw. (Hom., Aleyrodidae). Journal of Applied Entomology. 115: 37-

42.

Feng, R., and M. B. Isman. 1995. Selection for resistance to azadirachtin in the

green peach aphid, Myzus persicae. Experientia. 51: 831-833.

Fishpool, L. D. C., and C. Burban. 1994. Bemisia tabaci the whitefly vector of

African Cassava mosaic geminivirus. Tropical Science. 34: 55-72.

Refrences cited 112

Flint, H. M., and N. J. Sparks. 1989. Effect of azadirachtin from the neem tree

on immature sweetpotato whitefly, Bemisia tabaci (Homoptera:

Aleyrodidae) and other selected pest species on cotton. Journal of

Agricultural Entomology. 6: 211-215.

Foster, S. P., I. Denholm and A. L. Devonshire. 2000. The Ups and down of

insecticide resistance in peach-potato aphids (Myzus persicae) in the

UK. Crop Protection.19:873-879.

Gameel, O. I. 1974. Some aspects of the mating and oviposition behaviour of

the cotton whitefly Bemisia tabaci (Genn.). Revue de Zoologie

Africaine. 88: 784-788.

Giacomelli, G. A., and J. W. Roberts. 1993. Greenhouse covering systems.

HortTechnology. 3: 50-57.

Gill, R. J. 1990. The morphology of whiteflies. In: D. Gerling [ed.], Whiteflies,

their Bionomics, Pest status and Management. Intercept, Andover,

pp.13-46.

Goldsmith, T. H. 1993. Ultraviolet receptors and color vision: evolutionary

implication and a dissonance of paradigms. Vision Research. 34: 1479-

1487.

Gomaa, A. A., S. El-Sherif, and I. A. Hemeida. 1978. On the biology of the

potato tuber worm Phthorimea operculella Zeller (Lepidoptera:

Gelechiidae). Zeitschrift für angewandte Entomologie. 86:290-294.

Gomez, K. A., and A. A. Gomez. 1984. Statistical Procedures for Agriculture

Research. John Wiley and Sons, New York, USA.

Gonzalez, A. 2004. Viral Diseases Control with UV-Blocking Films in

Greenhouses of Southern Spain, International Symposium on

Protected Culture in a Mild-Winter Climate, Kissimmee, Florida.

Gonzalez-Zamora, J. E., D. Leira , M. J. Bellido, and C. Avilla. 2004. Evaluation of the effect of different insecticides on the survival and

capacity of Eretmocerus mundus Mercet to control Bemisia tabaci

(Gennadius) populations. Crop Protection. 23: 611-618.

Goulson, D., L. C. Derwent, D. I. Pernagos, and T. Williams. 2003. Effects of

optical brighteners included in bio-pesticide formulations on the growth

of crops. Agriculture, Ecosystems and Environment. 95: 235-240.

Refrences cited 113

Greathead, A. H. 1986. Host Plant. In M. J. N. Cock [ed.], Bemisia tabaci - A

Literature survey on the cotton whitely with an annotated bibliography.

CAB International Institutes, Biological Control, Silwood Park, UK. pp.

17-26

Greenough, D. R., L. L. Black, and W. P. Bond. 1990. Aluminum-surfaced

mulch: an approach to the control of tomato spotted wilt virus in

solanaceous crops. Plant Disease. 74: 805-808.

Handler, A. and T. Postlethwait. 1978. Regulation of vitellogenin synthesis by

ecdysone and juvenile hormone. Journal of Experimental Zoology.

247�254.

Hellpap, C. 1984. Effects of neem kernel extracts on the fall armyworm,

Spodoptera frugiperda. In: H. Schmutterer and K. R. S. Ascher [eds.],

Natural Pesticides from the neem tree (Azadirachta indica A. Juss) and

Other Tropical Plants: Proceedings of the second international neem

conference. German Agency for Technical Cooperation, Eschborn,

Germany, Rausichholzhausen, 1983, pp. 353-364.

Hilje, L. P. A. Stansly, M. Carballo, and G. A. Mora. 2003. Repellency and

deterrency caused by plant extracts on Bemisia tabaci adults. 3RD

International Bemisia Workshop, 17-20 March, Barcelona.

Hill, D. S. and J. M. Waller. 1991. Pests and diseases of tropical crops. Field

Handbook, 432 p.

Hill, T. A., and R. E. Foster. 2000. Effect of insecticides on the diamondback

moth (Lepidoptera: Plutellidae) and its parasitoids Diadegma insulare

(Hymenoptera: Ichneumonidae). Journal of Economic Entomology. 93:

763-768.

Hoddle, M. S., R. G. Van Driesche, and J. P. Sanderson. 1998. Biology and

use of the whitefly parasitoid Encarsia formosa. Annual Review of

Entomology.43: 645-69.

Refrences cited 114

Horowitz, A. R., and I. Ishaaya. 1996. Chemical control of Bemisia,

management and application. In: D. Gerling and R. T. Mayer [eds.],

Bemisia: 1995 taxonomy, biology, damage, control and management.

Intercept, Andover, United Kingdom, pp. 537-556.

Horowitz, A. R., Z. Mendelson, and I. Ishaaya. 1997. Effects of Abamectin

Mixed with Mineral Oil on the Sweetpotato Whitefly (Homoptera:

Aleyrodidae). Journal of Economic Entomology. 90: 349-353.

Horowitz, A. R., and I. Ishaaya. 1994. Managing resistance to insect growth

regulators in the sweetpotato whitefly (Homoptera: Aleyrodidae).

Journal of Economic Entomology. 87: 866�871.

Horowitz, A. R., and I. Ishaaya. 1996. Chemical control of Bemisia

management and application. In: Gerling, D., Mayer, R.T. (Eds.),

Bemisia: 1995 Taxonomy, Biology, Damage, Control and Management.

Intercept Ltd., Andover, Hants, UK, pp. 537�556.

Horowitz, A.R., I. Denholm, K. Groman, and I. Ishaaya. 1999a. Insecticide

resistance in whiteflies: current status and implication for management.

In: I. Denholm, P. Ioannidis, [eds.], Proceedings of an ENMARIA

Symposium: Combating Insecticide Resistance, Thessalonikis, Greece,

May 1999, pp. 8996�8998.

Horowitz, A.R., Mendelson, Z., Cahill, M., Denholm, and Ishaaya, I., 1999b. Managing resistance to the insect growth regulator, pyriproxyfen in

Bemisia tabaci. Pesticide Science. 55:272�276.

Immaraju, J. A., 1998. The commercial use of azadirachtin and its integration

into viable pest control programmes. Pesticide Science. 54: 285-289.

Ishaaya, I., S. Kontsedalov, D. Mazirov, and A. R. Horowitz. 2001. Biorational agents--mechanism and importance in IPM and IRM

programs for controlling agricultural pests. Meded Rijksuniv Gent Fak

Landbouwkd Toegep Biol Wet. 66: 363-74.

Refrences cited 115

Isman, M. B. 1994. Botanical insecticides. Pesticide Outlook 5 June: 26-31.

Isman, M. B. 1996. Some target and non-target effects of neem insecticides

(Abstract). International Neem Conference, 4-9 February, 1996,

Queensland, Australia.

Isman, M. B., O. Koul, J. T. Arnason, J. Stewart , and, G. S. Salloum. 1991. Developing a neem-based insecticide for Canada. Memoirs of the

Entomological Society of Canada. 159:39�47.

James, R. R. 2003. Combining Azadirachtin and Paecilomyces fumosoroseus

(Deuteromycotina: Hyphomycetes) to control Bemisia argentifolii

(Homoptera: Aleyrodidae). Journal of Economic Entomology. 96: 25-30.

Jinping, C., 1994. Processing tomato varietal trial (1994) In: ARC-AVRDC

Training Report. 12th

Regional Training Course in Vegetable Production

and research. Summary Report. JMPR (Joint FAO/WHO Meeting on

Pesticide Residues-Geneva) (2003).

Johnson, S., P. Dureja, and S. Dhingra. 2003. Photostablizers for

Azadirachtin-A (a Neem-based pesticide). Journal of Environmental

Science and Health. Part B. 38: 451-462.

Jones, D. R. 2003. Plant viruses transmitted by whiteflies. European Journal of

Plant Pathology.109: 195�219.

Jones, T., C. Scott-Dupree, R. Harris, L. Shipp, and B. Harris. 2005. The

Efficacy of spinosad against the western flower thrips Frankliniella

occidentalis, and its impact on associated biological control agents on

greenhouse cucumbers in south Ontario. Pest Management Science. 61:

179-185.

Joshi, B. G., and S. Sitaramaiah. 1979. Neem kernel as ovipositional repellent

for Spodoptera litura (F.) moths. Phytoparasitica. 7: 199-202.

Jungbluth, F. 1996. Crop Protection Policy in Thailand: economic and political

factors influencing pesticide use, Pesticide Policy Project,

GTZ/University of Hannover. Publication Series No. 5, Hannover,

December 1996, 75pp.

Kakar, K. L., J. P. Sharma, and G. S. Dogra. 1990. Feasibility of using

Trichogramma spp. against Heliothis armigera Hubner on tomato.

Indian Journal of Plant Protection. 18: 237-239.

Refrences cited 116

Keelberg, H. 1992. The NeemAzal conception: test of systemic activity. In: H.

Keelberg [ed.], Proceedings of the 1ST. Workshop on Practice Oriented

Results on Use and Production of Neem Ingredients. Druck and

Graphics, Giessen, Wetzlar, Germany.

Ketelaar, J. W., and P. Kumar. 2002. Vegetable Integrated Production and

Pest Management: The Case for Farmers as IPM Experts. International

Conference on Vegetables; ITC Hotel Windsor Sheraton and Towers,

Bangalore, India, 1-14 November 2002.

King, R. J., and M. K. Hennessey. 1996. Spinosad bait of the Caribbean fruit

fly (Diptera: Tephritidae). Florida Entomologist. 79: 526-531.

Kirchner, S. M., T. F. Doring, and H. Saucke. 2005. Evidence for trichromacy

in the green peach aphid, Myzus persicae (Sulz.) (Hemiptera:

Aphididae). Journal of Insect Pathology. 51: 1255-1260. Kontsedalov, S., P. G. Weintraub, A. R. Horowitz, and I. Ishaaya. 1998.

Effects of insecticides on immature and adult western flower thrips

(Thysanoptera: Thripidae) in Israel. Journal of Economic Entomology.

91: 1067-1071.

Koul, O., M. B. Isman., and C. M. Ketkar. 1990. Properties and usages of

neem Azadirachta indica. Canadian Journal of Botany. 68: 1-11.

Kring, J. B. 1972. Flight behaviour of aphids. Annual Review of Entomology.

17: 461-492.

Kring, J. B., and D. J. Schuster. 1992. Management of insects on pepper and

tomato with UV reflective mulches. Florida Entomologist. 75: 119-129.

Kumar, P., H.- M. Poehling, and C. Borgemeister. 2005. Effects of Different

Application Methods of Neem against Sweetpotato Whitefly Bemisia

tabaci Gennadius (Homoptera: Aleyrodidae) on Tomato plants. Journal

of Applied Entomology. 129:489�497.

Lange, W.H. and L. Bronson. 1981. Insect pests of tomato. Annual Review of

Entomology. 26:345�371.

Refrences cited 117

Larew, H. G. 1986. Use of neem seed extract in a developed country: Liriomyza

leafminer as a model case. In: H. Schmutterer and K.R.S. Ascher

[eds.], Proceedings of the 3RD. International Neem Conference on

Natural Pesticides from the Neem Tree and other Tropical Plant, 10-15

July, 1986. Deutsche Gesellschaft fuer Technische Zusammenarbeit

GmBH, Eschborn, Germnay., Kenya, Nairaobi.

Larew, H. G., 1988. Limited occurrences of foliar-, root and seed-applied neem

seed extract toxin in untreated plant parts. Journal of Economic


Larew, H. G., J. J. Kondel-Montz, R. F. Webb, and J. D. Warthen. 1985. Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) control on

chrysanthemum by neem-seed extract applied to soil. Journal of

Economic Entomology. 78, 80-84.

Lasota, J. A., and R. A. Dybas. 1990. Abamectin as a pesticide for agricultural

use. ACTA Leidensia (Leiden).59: 217-25.

Leskovar, D. I., and A. K. Boales. 1996. Azadirachtin: potential use for

controlling lepidopterous insects and increasing marketability of

cabbage. HortScience.31: 405-409.

Lindquist, R. K., and M. L. Casey. 1990. Evaluation of oils, soaps and natural

product derivatives for leaf miner, fox glove aphids, western flower

thrips and greenhouse whitefly control. Ohio Flower Association

Bulletin. 727: 3-5.

Liu, T. X., and P. A. Stansly. 1995. Deposition and Bioassay of insecticides

applied by leaf dip and spray tower against Bemisia agentifolii nymphs

(Homoptera: Aleyrodidae). Pesticide Science. 44: 317-322.

Liu, T., A. N. Sparks, W. H. Hendrink, and B. Yue. 1999. Effects of SpinTor

(spinosad) on cabbage looper (Lepidoptera: Noctuidae): Toxicity and

persistence of leaf residue on cabbage under field and laboratory

conditions. Journal of Economic Entomology. 92: 1266-1273.

Ludlum, C. T. and K. P. Sieber. 1988. Effect of azadirachtin on oogenesis in

Aedes aegypti. Physiological Entomology. 13: 177�184.

Ludwig, S., and R. Oetting. 2001. Effect of Spinosad on Orius indidiosus

(Hemiptera: Anthocoridae) when used for Frankliniella occidentalis

Refrences cited 118

(Thysanoptera: Thripidae) control on greenhouse pot

Chrysanthemums. Florida Entomologist. 84: 311-313.

Madhavi, D. L. and D. K. Salunkhe. 1998. Tomato. In: Handbook of Vegetable

Science and Technology. D.K Salunkhe and S.S. Kadam [eds]. Marcel

Dekker, New York, pp. 171-201.

Markham, P. G., I. D. Bedford, S. Liu, and M. S. Pinner. 1994. The

transmission of geminiviruses by Bemisia tabaci. Pesticide Science. 42:

123-128.

Martin, J. H. 1999. The whitefly fauna of Australia (Sternorrhyncha:

Aleyrodidae): a taxonomic account and identification guide.

Commonwealth Scientific and Industrial Research Organization,

Canberra, Australia (CSIRO Entomology Technical Paper No. 38),

197pp.

Martin, J. H., D. Mifsud, and C. Rapisarda. 2000. The whiteflies (Hemiptera:

Aleyrodidae) of Europe and the Mediterranean basin. Bulletin of

Entomological Research. 90:407�448.

Matsui, M. 1992. Irregular ripening of tomato fruit caused by the sweetpotato

whitefly, Bemisia tabaci (Gennadius) in Japan. Japanese Journal of

Applied Entomology and Zoology 36: 47-49. (In Japanese with English

Summary).

Matteson, N., and L. I. Terry. 1992. Response to colour by male and female

Frankliniella occidentalis. Entomologia Experimentalis et Applicata. 63:

187-201.

Matteson, N., I. Terry, A. Ascoli-Christensen, and C. Gilbert. 1992. Spectral

efficiency of the western flower thrips, Frankliniella occidentalis. Journal

of Insect Physiology. 38:453�459.

Mayes, M. A., G. D. Thompson, H. B., and M. M. Miles. 2003. Spinosad

toxicity to pollinators and associated risk. Reviews of Environmental

Contamination and Toxicology. 179: 37-71.

Refrences cited 119

Maynard, D. N., and D. J. Cantliffe. 1989. Squash silverleaf and tomato

irregular ripening: new vegetable disorders in Florida. University of

Florida, Cooperative Extension Service, Vegetable Crops Fact Sheet

VC-37.

Mazza, C. A., M. M. Izaguirre, J. Zavala, A. L. Scopel, and C. L. Ballaré. 2002. Insect perception of ambient ultraviolet-B radiation. Ecology

Letters. 6:722. Mazza, C. A., J. Zavala, A. L. Scopel, and C. L. Ballare. 1996. Perception of

solar UVB radiation by phytophagous insects: Behavioral responses

and ecosystem implications. Proceedings of the National Academy of

Science of the United States of America. 96: 980-985. McLeod, P., F. J. Diaz, and D. T. Johnson. 2002. Toxicity, persistence, and

efficacy of spinosad, chlorfenapyr, and thiamethoxam on eggplant

when applied against the eggplant flea beetle (Coleoptera:

Chrysomelidae). Journal of Economic Entomology. 95: 331-5.

McMichael, L. A., D. M. Persley, and J. E. Thomas. 2002. A new tospovirus

serogroup IV species infecting capsicum and tomato in Queensland.

Australian Plant Pathology 31: 231-239.

Meisner, J., K. R. S. Ascher., and R. Aly. 1982. The residual effect of some

products of neem seed on larvae of Spodoptera littoralis in laboratory

and field trials. In: H. Schmutterer, K. R. S. Ascher and H. Rembold

[eds.], Natural Pesticides from the neem tree (Azadirachta indica A.

Juss). Proceedings of the 1ST. International Neem Conference,

Rottachegreen, 1980. German Agency for Technical Cooperation,

Eschborn, Germany, Eschborn, Germany, pp. 157-170.

Michelle, L. B., and J. R. Baker. 2000. Comparison of greenhouse screening

materials for excluding whitefly (Homoptera: Aleyrodidae) and thrips

(Thysanoptera: Thripidae). Journal of Economic Entomology. 93: 800-

804.

Miles, M., M. Mayes, and R. Dutton. 2002. The effects of spinosad, a naturally

derived insect control agent, to the honeybee (Apis melifera). Meded

Rijksuniv Gent Fak Landbouwkd Toegep Biol Wet. 67: 611-6.

Refrences cited 120

Mitchell, P. L., R. Gupta, A. K. Singh, and P. Kumar. 2004. Behavioural and

Developmental Effects of Neem Extracts on Clavigralla scutellaris

(Hemiptera: Heteroptera: Coreidae) and Its Egg Parasitoid, Gryon

Fulviventre (Hymenoptera: Scelionidae). Journal of Economic


Morandin, L. A., M. L. Winston, M. T. Franklin, and V. A. Abbott. 2005.

Lethal and sub-lethal effects of spinosad on bumblebees (Bombus

impatiens Cresson). Pest Management Science. (in Press).

Mound, L. A. 1962. Studies on the olfaction and colour sensitivity of Bemisia

tabaci (Genn.) (Homoptera: Aleyrodidae). Entomologia Experimentalis

et Applicata. 5: 99-104.

Mound, L. A., and S. H. Halsey. 1978. Whiteflies of the World: a Systematic

Catalogue of the Aleyrodidae (Homoptera) with Host Plant and Natural

Enemy Data. Wiley, New York.

Mruthyunjaya, and D. Jha. 1996. Economics and Policy Issues. In: Randhawa,

N. S. and B. S. Parmar, [eds.], Neem, Society of Pesticide Science,

India. New Age International (P) Limited, Publishers, New Delhi, India,

pp. 311-317.

Murai, T., S. Kawai, W. Chongratanameteekul, and F. Nakasuji. 2000. Damage to tomato by Ceratothripoides claratris (Shumsher)

(Thysanoptera: Thripidae) in central Thailand and a note on its

parasitoid, Goethena shakespearei Girault (Hymenoptera: Eulophidae).

Applied Entomology and Zoology. 35: 505-507.

Mutwiwa, N. M., C. Borgemeister, B. V. elsner, and H.-J. Tantau. 2005. Effects of UV-Absorbing Plastic Films on Greenhouse Whitefly

(Homoptera: Aleyrodidae). Journal of Economic Entomology. 98: 1221-

1228.

Nardo, E. A. B., A. S., De Costa, and A. L. Lourencao. 1997. Melia

Azedarach extract as an antifeedant to Bemisia tabaci (Homoptera:

Aleyrodidae). Florida Entomologist. 80: 92-94.

Nawrocka, B. 2002. Spinosad as a new compound for integrated control of

Franklineiella occidentalis Pergande on cucumber and tomato in

greenhouse. Integrated control in protected crops. IOBC/ Wprs.

Bulletin. 25: 201-203.

Refrences cited 121

Ochoa, P., and M. Carballo. 1993. Effect of various insecticides on Liriomyza

huidobrensis (Diptera: Agromyzidae) and its parasiotid Diglyphus isaea

Walker (Hymenoptera: Eulophidae). Manejo Integrado de Plagas

(Costa Rica). 26: 8-12.

Ossiewatsch, H. R. 2000. Zur Wirkung von Samenkern-Wasserextrakten des

Mienbaumes Azadirachta indica (A. Juss) auf Blattlaeuse und ihre

natuerlichen Gegenspieler, Ph.D. dissertation. Justus-Liebig University

Giesen, Germany.

Otto, D. 1994. Systemic effects of azadirachtin preparation NeemAzal W on

larvae and adults of Leptinotarsa decemlineata. In: H. Keelberg [ed.],

Proceedings of the 3RD. Workshop on Practice Oriented Results on Use

and Production of Neem Ingredients, 22-25 November 1993. Druck and

Graphics, Giessen, Germany. Wetzlar, Germany, pp. 39-53.

Oudejans, J. 1999. Studies on IPM Policy in SE Asia: Two centuries of plant

protection in Indonesia, Malaysia and Thailand, Wageningen

Agricultural University Papers, Backhuys Publishers, PO Box 321, 2300

AH Leiden, the Netherlands, 316pp.

Palumbo, J. C., A. R. Horowitz, and N. Prabhaker., 2001. Insecticidal control

and resistance management for Bemisia tabaci. Crop Protection.

20:739�765.

Palumbo, J. C., and W. E. Coates. 1996. Air-assisted electrostatic application

of pyrethroid and endosulfan mixtures for sweetpotato whitefly

(Homoptera: Aleyrodidae) control and spray deposition in cauliflower.

Journal of Economic Entomology. 89: 970�980.

Pietrantonio, P. V., and J. H. Benedict. 1999. Effect of new cotton insecticides

chemistries, tebufensoside, spinosad and chlorfenapyr on Orius

insidiosus and two Cotesia species. Southwestern Entomologist. 24:

21-29.

Refrences cited 122

Prabhaker, N., N. C. Toscano, and D. L. Coudriet. 1989. Susceptibility of the

immature and adult stages of the sweetpotato whitefly (Homoptera:

Aleyrodidae) to selected insecticides. Journal of Economic Entomology.

82: 983�988.

Prabhaker, N., N. C. Toscano, and T. J. Henneberry, 1999. Comparison of

Neem, Urea, and Amitraz as Oviposition Suppressants and Larvicides

Against Bemisia argentifolii (Homoptera: Aleyrodidae). Journal of

Economic Entomology. 92: 40-46.

Prabhaker, N., N. C. Toscano, and T. J. Henneberry. 1998. Evaluation of

insecticide rotations and mixtures as resistance management strategies

for Bemisia argentifolii (Homoptera: Aleyrodidae). Journal of Economic


Prabhaker, N., N. C. Toscano, S. J. Castle, and T. J. Henneberry. 1997. Selection for imidacloprid resistance in silverleaf whiteflies from the

Imperial Valley and development of a hydroponics bioassay for

resistance monitoring. Pesticide Science. 51: 419�428.

Pradhan, S., and M. G. Jotwani. 1968. Neem as insect deterrent. Chemical

Age, India. 19: 756-759.

Premachandra, W. T. S. D. 2004. Biology, population dynamics, vector

potential and management of Ceratothripoides claratris on tomatoes in

central Thailand. Institute of Plant Protection and Plant Diseases. PhD

dissertation, University of Hanover, Germany, Hanover, pp. 140.

Premachandra, W. T. S. D., C. Borgemeister, and H.-M. Poehling. 2005. Effects of Neem and Spinosad on Cetraothripoides claratis

(Thysanoptera: Thripidae), an Important Vegetable Pest in Thailand,

Under Laboratory and Greenhouse Conditions. Journal of Economic


Price, J. F., and D. J. Schuster. 1991. Effects of natural and synthetic

insecticides on sweetpotato whitefly Bemisia tabaci (Homoptera;

Aleyrodidae) and its hymenopteran parasitoids. Florida Entomologist.

74: 60-68.

Puri, S. N., B. B. Bhosle, M. Ilyas, G. D. Bulter, and T. J. Henneberry. 1994. Detergents and plant-derived oils for control of the sweetpotato whitefly

on cotton. Crop Protection. 13: 45-48.

Refrences cited 123

Quaintance, A. L. 1900. Contribution towards a monograph of the American

Aleyrodidae. US Department of Agriculture, Technical Service, Bureau

of Entomology. 8: 9�64.

Rao, P. J., S. Gupta, D. M. Raj, K. R. Kranthi. 1996. Neem effects on

Spodoptera litura (Fab.): a holistic study. In: R. P. Singh, M. S. Chari,

A. K. Raheja, W. Kraus [eds.], Neem and Environment. Proceeding of

1ST. World Neem Conference, India. Oxford and IBH Publ. Co., pp.

357�374.

Rapisarda, C., and G. T. Garzia. 2002. Tomato yellow leaf curl Sardinia virus

and its vector Bemisia tabaci in Sicilia (Italy): present status and control

possibilities OEPP/EPPO. Bulletin OEPP/EPPO Bulletin. 32: 25-29.

Ray, D. E. 1991. Pesticides derived from plants and other organisms. In: W. J.

Hayes, Jr. and E. R. Laws, Jr., [eds.], Handbook of Pesticide

Toxicology. Academic Press, New York, NY, 1991, New York, pp. 10-

144.

Reis, P. R., M. P. Neto., R. A. Franco., A. V. Teodoro. 2004. Control of

Brevipalpus phoenicis (Geijskes, 1939) and Oligonychus ilicis

(McGregor, 1917) (Acari: Tenuipalpidae, Tetranychidae) in coffee

plants and the impact on beneficial mites. I - Abamectin and

emamectin. Ciênc. agrotec., Lavras, 28:269-281. (in Sapnish).

Rembold, H.1988. Isomeric azadirachtin and their mode of action. In: M.

Jacobson, Boca Raton [eds.], Focus on Phytochemical Pesticides, Vol.

1, The Neem Tree. CRC Press, pp. 47�67.

Reuveni, R., and M. Raviv. 1992. The effect of spectrally modified

polyethylene films on the development of Botrytis cinerea in

greenhouse grown tomato plants. Biological Agriculture and

Horticulture. 9: 77-86.

Reuveni, R., and M. Raviv. 1997. Manipulation of light for the management of

foliar pathogens of greenhouse crops. The story of the establishment of

a new discipline., International Congress for Plastics in Agriculture.

CIPA Proceedings, Tel Aviv, Israel., pp. 269-281.

Riddell-Swan, J. M., 1988. Crop protection. In: Hong Kong. Annual

Departmental report by the Director of Agriculture; and Fisheries for the

financial year 1985-86, pp 12-13.

Refrences cited 124

Riley, D. G., and J. C. Palumbo. 1995. Interaction of silverleaf whitefly

(Homoptera: Aleyrodidae) with cantaloupe yield. Journal of Economic

Entomology. 88:1726�1732.

Rossel, S., and R. Wehner. 1984. Celestial orientation in bees: the use of

spectral cues. Journal of Comparative Physiology A. 155: 605-613.

Rubinstein, G., S. Morin, and H. Czosnek. 1999. Transmission of tomato

yellow leaf curl geminivirus to imidacloprid treated tomato plants by the

whitefly Bemisia tabaci (Homoptera: Aleyrodidae). Journal of Economic

Entomology. 92: 658�662.

Saha, P. K. 1993. Overview of pest control in Asia. In: APO Pest Control in Asia

and the Pacific, Report on an APO Seminar. Asian Productivity

Organization (APO), Tokyo, pp. 42.

Salgado, V. L. 1997. The modes of action of Spinosad and other insect control

products. Down to Earth 52: 35-43.

Salgado, V. L. 1998. Studies on the mode of action of Spinosad: insect

symptoms and physiological correlates. Pesticide Biochemistry and

Physiology. 60: 91-102.

SAS Institute. 1999. SAS/Stat user�s guide, version 8, SAS Institute, Cary, NC.

Saunders, D. G., and B. L. Bret. 1997. Fate of spinosad in the environment.

Down to Earth 52: 14-20.

Saxena, R. C. 1989. Insecticides from neem. In :J. T. Arnasan, B. J. R.

Philogene and P. Morand [eds.], Insecticides from plants. ACS

Symposium Series, American Chemical Society, Washington, DC, pp.

110-135.

Saxena, R. C., G. P. Waldbauer., N. J. Liquido., and B. C. Puma. 1982. Effects of neem seed oil on the rice leaf folder, Cnaphalocrocis

medinalis. In: H. Schmutterer, K. R. S. Ascher and H. Rembold [eds.],

Natural Pesticides from the neem tree (Azadirachta indica A. Juss).

Proceedings of the 1ST. international neem conference, Rottachegreen,

1980. German Agency for Technical Cooperation, Eschborn, Germany,

Eschborn, Germany, pp. 189-204.

Refrences cited 125

Sawangjit, S., O. Chatchawankanphanich, P. Chiemsombat, T. Attathom, J. Dale, S. Attathom. 2005. Possible recombination of tomato-infecting

begomoviruses in Thailand. Journal of General Plant Pathology. 71:

314 � 318.

Scherer, C., and G. Kolb. 1987. Behavioural experiments on the visual

processing of color stimuli in Pieris brassicae L. (Lepidoptera). Journal of

Comparative Physiology . A. 160: 647-656.

Schmutterer, H. 1985. Which insect pest can be controlled by application of

neem seed kernel extract under field conditions? Zeitschrift fuer

Angewandte Entomologie. 100: 468-775.

Schmutterer, H. 1988. Potential of Azadirachtin-containing pesticides for

integrated pest control in developing and industrialized countries.

Journal of Insect Physiology. 34: 713-719.

Schmutterer, H. 1990. Properties and potential of natural pesticides from neem

tree, Azadirachta indica. Annual Review of Entomology. 35: 271-297.

Schmutterer, H. 1995. The Neem Tree, VCH, Weinheim, Germany.

Schoonejans, T., and M. Van der Staaij. 2001. Spinosad, a new tool for insect

control in vegetables cultivated in greenhouses. Meded Rijksuniv Gent

Fak Landbouwkd Toegep Biol Wet. 66: 375-86.

Schulz, W. D., and U. Schluter. 1984. Structural damages caused by neem in

Epilachna varivestis. In: H. Schmutterer, K. R. S. Ashcher [eds.] A

summary of histological and ultrastructural data II. Tissues affected in

adults. In: Proceedings of Second International Neem Conference

(1983). Germany: Rauischholzhausen, pp. 237�252.

Schuster, D. J., and P. H. Everatt. 1983. Response of Liriomyza trifolii

(Diptera: Agromyzidae) to insecticides on tomato. Journal of Economic


Schuster, D. J. 1993. Management of the sweetpotato whitefly and geminivirus

on fresh market tomatoes in west-central Florida fall 1991. Insecticide

Acaricide Tests. 18:180�181.

Schuster, D. J. 1994. Insect control on fresh market tomatoes in west-central

Florida, spring 1993. Arthropod Management Tests. 19:150�152.

Refrences cited 126

Schuster, D. J. 1995a. Control of insects on fresh market tomatoes in west-

central Florida, spring 1994. Arthropod Management Tests. 20: 134�

136.

Schuster, D. J. 1995b. Insect control on bell pepper in west-central Florida,

spring 1994. Arthropod Management Tests. 20:103�104.

Schuster, D. J. 1996. Insect management on fresh market tomatoes in west-

central Florida, spring 1995. Arthropod Management Tests. 21:185�

186.

Schuster, D. J. 1997. Management of insects on fresh market tomatoes, spring

1996c. Arthropod Management Tests. 22:184�185.

Schuster, D. J. 1998. Management of whiteflies, bugs, and leafminers on fresh

market tomatoes, fall 1996. Arthropod Management Tests. 23:156�

157.

Schuster, D. J., 2000a. Insecticides applied on demand for managing the

silverleaf whitefly on fresh market tomatoes in spring 1998. Arthropod

Management Tests. 25: 100.

Schuster, D. J., 2000b. Insecticides applied on demand for managing the

silverleaf whitefly on fresh market tomatoes in fall 1998. Arthropod

Management Tests. 25: 101.

Schuster, D. J., and J. E. Polston. 1997a. Management of insect on fresh

market tomatoes spring 1996B. Arthropod Management Tests. 22:

183�184.

Schuster, D. J., and J. E. Polston. 1997b. Management of whiteflies and

armyworm on fresh market tomatoes fall 1995. Arthropod Management

Tests. 22: 182�183.

Schuster, D. J., and J. E. Polston. 1998. Insect management on fresh market

tomatoes spring 1997B. Arthropod Management Tests. 23: 159�160.

Schuster, D. J., T. F. Mueller, J. B. Kring, and J .F. Price. 1990. Relationship

of the sweetpotato whitefly to a new tomato fruit disorder in Florida.

Hortscience. 25: 1618-1620.

Scott, S. J., P. J. McLeod, F. W. Montgomery, and C. A. Hander. 1989. Influence of reflective mulch on incidence of thrips, (Thysanoptera:

Thripidae: Phlaeothripdae) in staked tomatoes. Journal of

Entomological Science. 24: 422-427.

Refrences cited 127

Scott, I. M., and N. K. Kaushik.2000. The Toxicity of a Neem Insecticide to

Populations of Culicidae and Other Aquatic Invertebrates as Assessed

in In Situ Microcosms. Archives of Environmental Contamination and

Toxicology. 39: 329�336.

Secker, A. E., I. A. Bedford, P. G. Markham, and M. E. C. William. 1998. Squash, a reliable field indicator for the presence of B biotype of

tobacco whitefly, Bemisia tabaci, Brighton Crop Protection Conference-

Pest and Diseases. British Crop Protection Council, Farnham, UK. pp.

837-842,

Shelton A.M., W.T. Wilsey, and M.A. Schmaedick. 1998. Management of

onion thrips (Thysanoptera: Thripidae) on cabbage by using plant

resistance and insecticides. Journal of Economic Entomology. 91: 329-

333.

Showler, A. T., S. M. Greenberg., and J. T. Arnason. 2004. Deterrent Effects

of Four Neem-Based Formulations on Gravid Female Boll Weevil

(Coleoptera: Curculionidae) Feeding and Oviposition on Cotton

Squares. Journal of Economic Entomology. 97: 414-421.

Sieber, K. P., and H. Rembold. 1983. The effects of azadirachtin on the

endocrine control of moulting in Locusta migratoria. Journal of Insect

Pathology. 29: 523�527.

Singh, R. P. 1993. Botanical pesticides in developing countries: current status

and future trends. In: G. S. Dhaliwal and S. Balwinder [eds.],

Pesticides, their ecological impact in developing countries.

Commonwealth Publishers, New Delhi, India, pp. 236-269.

Sparks, T. C., G. D. Crouse, and G. Durst. 2001. Natural products as

insecticides: the biology, biochemistry and quantitative structure-activity

relationships of spinosyns and spinosoids. Pest Management Science.

57: 896-905.

Sparks, T. C., G. D. Thompson, H. A. Krist, M. B. Hertlein, L. L. Larson, T. V. Worden, and S. T. Thibault. 1998. Biological activity of the

spinosyns, new fermentation derived insect control agents, on tobacco

budworm, (Lepidoptera: Noctuidae) larvae. Journal of Economic

Entomology. 91: 1277-1283.

Refrences cited 128

Stansly, P.A., and B. M. Cawley. 1994. Control of adult sweetpotato whitefly

(SPWF) and tomato mottle geminivirus (TMoV) transmission on staked

tomato, spring, 1992. Arthropod Management Tests. 19:156. Stansly, P.A., and J. M. Conner. 1995. Control of silverleaf whitefly and

tomato pinworm on staked tomato with chemical and biological

insecticides, spring 1994. Arthropod Management Tests. 20: 145�146.

Stansly, P.A., and J. M. Conner. 1998. Control of silverleaf whitefly on staked

tomato with foliar and soil-applied systemic insecticides, 1997.

Arthropod Management Tests. 23: 165�166.

Stansly, P.A., and J. M. Conner. 2000. Impact of insecticides on silverleaf

whitefly and tomato yellow leaf curl virus on staked tomato, 1999.

Arthropod Management Tests. 25: 104.

Stansly, P.A., J. M. Conner and M. A. Pomerinke. 1999. Control of silverleaf

whitefly on staked tomato with foliar insecticides. Arthropod

Management Tests. 24:183�184.

Stapleton, J. J., and C. G. Summers. 2002. Reflective mulches for

management of aphids and aphid-borne virus diseases in late-season

cantaloupe (Cucumis melo L. var.cantalupensis). Crop Protection. 21:

891-898.

Stavisky, J., J. Founderburk, B. V. Brodbeck, S. M. Olson, and P. C. Anderson. 2002. Population Dynamics of Frankliniella spp. and

Tomato Spotted Wilt Incidence as Influenced by Cultural management

Tactics in Tomato. Journal of Economic Entomology. 95: 1216-1221.

Steel, R. G. D., and Torrie, J. H. 1980. Principles and Procedures of Statistics,

2nd Edn. McGraw Hill, Inc, New York.

Stokes, J. B., and R. E. Redfern. 1982. Effect of sunlight on Azadirachtin:

antifeeding potency. Journal of Environmental Science and Health.

Part: A. 17: 57-65.

Stone, R. 1992. A biopesticidal tree begins to blossom. Science (Wash. D.C.)

255: 1070-1071. Summers, C. G., and J. J. Stapleton. 1998. Management of vegetable insects

using plastic mulch: 1997 season review. U.C. Plant Protection

Quarterly 8: 9-11.

Refrences cited 129

Summers, C. G., J. P. Mitchell, and J. J. Stapleton. 2004. Management of

Aphid-Borne Viruses and Bemisia argentifolii (Homoptera: Aleyrodidae)

in Zucchini Squash by Using UV Reflective Plastic and Wheat Straw

Mulches. Environmental Entomology. 33: 1447-1457.

Sundaram, K. M. S. 1996. Azadirachtin biopesticide: a review of studies

conducted on its analytical chemistry, environmental behavior and

biological effects. Journal of Environmental Science and Health. Part B:

31:913�948.

Suwwan, M. A., M. Akkawi, A. M. Al-Musa, and A. Mansour. 1988. Tomato

performance and incidence of tomato yellow leaf curl (TYLC) virus as

affected by type of mulch. Scientia Horticulturae. 37: 39�45.

Suzuki, H., and A. Miyara, 1984. Integrated control of Thrips palmi using

agricultural covering materials. (I) Loss assessment on cucumber in

Japan. Proceedings of the Association for plant Protection of Kyushu.

30:135-139 (in Japanese).

Talekar, N. S., and A. M. Shelton. 1993. Biology, ecology and management of

the diamond back moth. Annual Review of Entomology. 38: 275-301.

Tanapas, V., P. Poolpol, T. Sutabutra and S. Attathom 1983. Some

properties of the causal agent of tomato yellow leaf curl disease.

Kasetsart Journal (Natural Science) 17: 80-89.

Taylor, I. B. 1986. Biosystematics of the Tomato, In: The Tomato Crop. A

Scientific Basis for Improvement. J. Atherton and G. Rudich [eds.]

Chapman and Hall, New York, pp.1-34.

Terry, L. I. 1997. Host selection, communication and reproductive behaviour.

In: T. Lewis [ed.], Thrips as Crop Pests. CAB International, New York,

pp. 65�118.

Thoeming, G., C. Borgemeister, M. Sétamou, and H.-M. Poehling. 2003. Systemic Effects of Neem on Western Flower Thrips, Frankliniella

occidentalis (Thysanoptera: Thripidae). Journal of Economic


Thompson, G. D., R. Dutton, and T. C. Sparks. 2000. Spinosad-a case study:

an example from a natural products discovery programme. Pest

Management Science. 56: 696-702.

Refrences cited 130

Thongrit, D., S. Attathom and T. Sutabutra. 1986. Tomato yellow leaf curl

virus in Thailand. FFTC Book Series No. 33. Taiwan. Republic of

China.

Tindall, H. D. 1983. Vegetables in the tropics. English Language Book Society,

Macmillan. 533 p.

Tjosvold, S. A., and W. E. Chaney. 2001. Evaluation of reduced risk and other

biorational miticides on the control of spider mites (Tetraanychus

urticae). Acta Horticulturae. 547: 93-96.

van Lenteren, J. C. 1983. Potential of entomophagous parasites for pest

control. Agriculture, Ecosystems and Environment. 10: 143-158.

van Lenteren, J. C., P. M. J. Ramakers, and J. Woets. 1980. World situation

of biological control in greenhouse, with special attention to factors

limiting application. Mededelingen Faculteit Landbouwwetenschappen

Rijksuniversiteit Gent. 537-544.

Vernon, R. S., and D. R. Gillespie. 1990. Spectral responsiveness of

Frankliniella occidentalis (Thysanoptera: Thripidae) determined by trap

catches in greenhouses. Environmental Entomology. 19: 1229-1241.

von Elling, K., C. Borgemeister, M. Setamou, and H.-M. Poehling. 2002. The

effect of NeemAzal- T/S, a commercial neem product, on different

development stages of the common greenhouse whitefly Trialeurodes

vaporariorum Westwood (Hom., Aleyrodidae). Journal of Applied


Vos, J. G., M. T. S. Uhan, and R. Sutarya. 1995. Integrated crop management

of hot pepper (Capsicum spp.) under tropical lowland conditions:

effects of rice straw and plastic mulches on crop health. Crop

Protection. 4: 445-452.

Walter, J. F., 1999. Commercial experience with neem products. In: F. R. Hall

and J. J. Menn [eds]., Methods in Biotechnology. Vol. 5: Biopesticides.

Humana Press, Totowa, NJ, Totowa, NJ, p.155-170.

Wang, K. Y., X. B. Kong, X. Y. Jiang, M. Q. Yi, and T. X. Liu. 2003. Susceptibility of immature and adult stages of Trialeurodes

vaporariorum (Hom., Aleyrodidae) to selected insecticides. Journal of

Applied Entomology. 127: 527�533.

Refrences cited 131

Webb, R. E., M. A. Hinebaugh, R. K. Lindquist, and M. Jacobson. 1983. Evaluation of aqueous solution of neem seed extract against Liriomyza

trifolii (Burgess) and L. sativae Blanchard (Diptera: Agromyzidae).


Weintraub, P.G., and A. R. Horowitz. 1997. Systemic effects of a neem

insecticide on Liriomyza huidobrensis larvae. Phytoparasitica. 25: 283-

289.

Weintraub, P. G., and A. R. Horowtiz. 1997. Systemic effects of a neem

insecticide on Liriomyza huidobrensis larvae. Phytoparasitica. 25: 283-

289.

Williams III, L., L. D. Price, and V. Manrique. 2003. Toxicity of field-weathered

insecticide residues to Anaphes iole (Hymenoptera: Mymaridae), an

egg parasitoid of Lygus lineolaris (Heteroptera: Miridae), and

implications for inundative biological control in cotton. Biological Control

26: 217-223.

Williams, L. and T. J. Dennehy. 1996. Whitefly control in Arizona: developing

a resistance management program for imidacloprid. Resistant Pest

Management. 8: 48-52.

Wislocki, P. G., L. S. Grosso, and R. A. Dybas. 1989. Environmental aspects

of abamectin use in crop protection. In: W. C. Campbell [ed.],

Ivermectin and Abametin. Springer Verlag, New York, NY, New York,

pp. 10-146.

Xu, R. M., Q. R. Zhu, and Z. L. Zhang. 1984. A system approach to

greenhouse whitefly Trialeurodes vaporariorum population dynamics

and strategy for greenhouse whitefly control in China. Zeitschrift fuer

Angewandte Entomologiel. 97: 305-313.

Yokomi, R. K., L. S. Osborne and K. A. Hoelmer. 1990. Relationship between

the sweetpotato whitefly and the squash silverleaf. Phytopathology. 80:

895-900.

Zchori-Fein, E., R. T. Roush, and J. P. Sanderson. 1994. Potential for

Integration of Biological and Chemical Control of Greenhouse Whitefly

(Homoptera; Aleyrodidae) Using Encarisa formosa (Hymenoptera:

Aphelenidae) and Abamectin. Environmental Entomology. 23: 1277-

1282.

Refrences cited 132

Zhao, J. Z., Y. X. Li, H. L. Collins, L. Gusukuma-Minuto, R. F. Mau, G. D. Thompson, and A. M. Shelto. 2002. Monitoring and characterization

of diamondback moth (Lepidoptera: Plutellidae) resistance to spinosad.



Acknowledgements

My sincere thanks and gratitude to Professors, Dr. Hans-Michael Poehling

(Supervisor) and Dr. Christian Borgemeister for giving me the opportunity to

perform this research work in the framework of the FOR 431 project �Protected

cultivation - an approach to sustainable vegetable production in the humid

tropics�. I am greatly indebted to Professor Dr. Hans-Michael Poehling for his

supervision especially during the period of preparation of manuscripts and

thesis assembling, and particularly for the tedious editing work in preparing the

manuscripts in this dissertation. In addition, my sincere thanks to Professor Dr.

Christian Borgemeister for his invaluable comments and suggestions during the

first 2 years of my work with the project. I am also grateful to Prof. Dr. Hans-

Jürgen Tantau, Director, Institute of Horticultural and Agricultural Engineering

(ITG), Hannover University, for providing support and advice on the UV part of

the work and also for accepting the co-supervision of this dissertation.

Gratitude to Dr. Maxwell J. Whitten for constant encouragement and support

that provided opportunity to learn about vegetable smallholders in South and SE

Asia and elsewhere. Thanks to all vegetable farmers in India, Bangladesh,

Thailand, Laos, Vietnam, China, PR and elsewhere for providing constant

inspiration to find better ways to mange crops and pests. Thanks once again to

Max for reading and commenting on all manuscripts of this dissertation.

Sincere thanks goes to Mr. Jan Willem Ketelaar, Chief Technical Advisor/IPM

Expert of the Regional Vegetable IPM Programs and a good friend for his

invaluable support and encouragements.

I am very much grateful to Dr. Paul Debarro, CSIRO, Australia for providing

information on the species details of the Bemisia specimen and to Dr. Kurapan

Kittipakorn (Department of Agriculture, Bangkok, Thailand) for providing the

initial culture of whitefly. Also, sincere thanks go to Dr. Stefan Schmidt,

Hymenoptera Section, Zoologische Staatssammlung Muenchen,

Muenchhausenstr. 21, 81247 Munich, Germany for kindly identifying the

parasitoids species more then once.


I am also grateful to Dr. E. Hummel of Trifolio-M GmbH (Lahnau, Germany) for

providing the two neem products and their blank formulations. My special

thanks go to Professor Dr.-Ing. Burkhard von Elsner, Institut fuer Technik in

Gartenbau und Landwirtschaft, Universitaet Hannover, for kind assistance in

measuring the spectral transmissivity of lots of plastic and net samples over the

years and for timely advices throughout the UV trials.

Sincere thanks and gratitude to Prof. V. M. Salokhe, Coordinator, ASE Program

(AIT, Bangkok) for providing constant encouragement and support towards

making available brand new laboratory (ENTOMOLOGY LABORAOTRY II;

WHITEFLY LAB) for research work, where I carried out most of my research

and write-ups and once again his support in procuring the greenhouse

structures for the UV-related experiments.

I am very much thankful to previous and present project coordinators; Dr.

Thomas Achilles and Dr. Johannes Max respectively, for their great logistic

support during the entire periods of my research. My special thanks to Mr.

Lakchai Meenakanit (senior project consultant, AIT) and Ms. Patcharee

Meenakanit (Ex Department of the Agriculture Extension, Bangkok, Thailand)

for their great logistic support extended to me during the research work. I highly

appreciate and I am thankful for the technical assistance provided to me by Ms.

Janjira, Ms. Sopana, Mr. Swat, Mr. Songtham, Mr. Ganesh (AIT master student)

and to all daily wage workers at AIT-Hanover Project. Moreover, I would like to

thank all my friends in the FOR 431 project for their support and encouragement

throughout the research.

I am highly grateful to the German Research Council (DFG) and the IPP of

Hanover University for financial support of this research.

Last but not least, I would like to express my deepest gratitude to my wife, Abha

Mishra for her immense support on every matter related to research and

managing family. Without her support it could have been impossible to complete

this research and dissertation. My love goes to my daughters� duo; Vagisha and

Tanvi for making life colorful and happy amidst extremely hectic times during


research and later write-ups. My sincere regards goes to my father, Professor

Dr. Sundareshwar Mishra and mother, Smt. Usha Mishra and my siblings

Prashant, and two sisters Pratibha and Prabha and their families for their

unconditional love and support to reach to this point in life.

I would also like to thank my all teachers in institutions from where I acquired

basic knowledge eg. Tirhut College of Agriculture, Dholi, Muzaffarpur (Rajendra

Agriculture University, Pusa, Samastipur, India) during undergraduate studies;

Asian Institute of Technology, Bangkok, Thailand during M. Sc. studies.

Especially to Drs. Steffen Johnsen (presently Advisor, CDC, Cambodia) and

Prof. Dr. Richard L. Tinsley (Dick Tinsley) for their support during M.Sc. studies

at AIT, Thailand.

Finally, prayers to the almighty God (the Cosmic Consciousness); who

constantly provided inspiration to remain steadfast to the goals to serve

humanity in all form and manifestation.

Aum. That unmanifested Brahman is perfect, and This manifested Brahman is

also perfect. Fullness proceeds from fullness. Taking fullness from fullness, all

that remains is fullness.

Knowledge and ignorance, he who knows the two together crosses death

through ignorance and attains life eternal through knowledge.

(Isha Upanishad; Verse 11)

!!!Aum Peace! Peace! Peace!!!

Curriculum Vitae 136

Curriculum vitae Personal Data Name Prabhat Kumar Date of Birth 27.12.1970 Place of Birth Muzaffarpur, India Family status Married with 2 (two) children Education Background 1989 � 1993 B.Sc. (Agriculture & Hons.), Tirhut Collage of Agriculture,

Rajendra Agriculture University, Pusa, India 1995� 1996 M. Sc. (Agricultural Systems), Asian Institute of Technology,

Thailand. 2002 � 2005 PhD. Institute of Plant Protection and Plant Diseases,

University of Hannover, Germany Scholarship, Awards and Honours

• Ranked first (1/80) in the class of B. Sc. (Ag.). • Awarded the Keidanren Foundation Fellowship, Japan for Master�s study at Asian

Institute of Technology, Bangkok (January 1995- August 1996). • Awarded MERIT Scholarship for the outstanding academic performance in B. Sc. (Ag). • Awarded Thesis Research Grant from DANIDA for conducting master�s thesis research

Work Experience 1997 – 2001 Resident Vegetable IPM Consultant, Food & Agril. Organization of the

United Nations (FAO), Bangladesh, Thailand, Lao PDR, Cambodia and Vietnam.

2001 – 2002 Senior Farming System Specialist, AME (An Indo-Dutch bilateral Project), Bangalore, India.

2002 – 2005 Project Researcher, AIT-Hannover project for Sustainable Vegetable Production under the Protected Cultivation in the Humid Tropics, Thailand & PTD IPM Expert for Vegsys (EU-China-Vietnam) Project.

Publications • Tinsely, R. L., P. Kumar, and D.T.T. Huyen. 1998. Chemical usages on Vegetables in

Asia. Workshop on Sustainability of Horticulture Systems in Southeast Asia, AIT, Thailand, 1-3 April, 1998.

• Kumar, P., S. Johnsen and R. L. Tinsley. 2000. Life Cycle Studies on Fruit and Shoot borer (Leucinodes orbonalis; Pyralidae; Lepidopetra) and natural enemies of eggplant (Solanum melongena) insect-pests, Journal of Applied Biology, Vol. 10 (2), 2000.

• Kumar, P., S. Johnsen and R. L. Tinsley. 2000. Effect of Insecticide on population of fruit and shoot borer (Leucinodes orbonalis Gness; Pyralidae; Lepidopetra) secondary pests and natural enemies of eggplant (Solanum melongena), Journal of Applied Biology, Vol. 10 (1), 2000.

• Kumar, P., S. Johnsen and R. L. Tinsley. 2000. Insecticide use in eggplant (Solanum melongena) and related extension issues in Indo-Gangetic plains of North Bihar, Journal of Applied Biology, Vol. 10 (1), 2000.

• Ketalaar, J. W. K., and P. Kumar. 2002. Vegetable Integrated Production and Pest Management: the case for farmers as IPM Expert. International Conference on Vegetables held at the ITC Hotel Windsor Sheraton and Towers, Bangalore, India, 11-14 November 2002.

• Kumar, P., H.- M. Poehling, and C. Borgemeister. 2005. Effects of Different Application Methods of Neem against Sweetpotato Whitefly Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) on Tomato plants. Journal of Applied Entomology. 129:489�497.

Contribution in Book

• Tinsley, R. L. 2004. Developing Smallholder Agriculture: A Global Approach, AgBe Publishing, Brussels, Belgium. Contributor: Chapter 6 Sustainability of Smallholder Agriculture.

Curriculum Vitae 137

Lebenslauf Persönliche Daten Name: Prabhat Kumar Geburtsdatum: 27.12.1970 Geburtsort: Muzaffarpur, Indien Familienstand: Verheiratet, zwei Kinder Ausbildung 1989 � 1993 B.Sc. Landwirtschft, Tirhut Collage of Agriculture, Rajendra Agriculture

University, Pusa, Indien. 1995� 1996 M. Sc. (Agricultural Systems), Asian Institute of Technology, Thailand. 2002 � 2005 Doktorand, �Institut für Pflanzenschutz und Pflanzenkrankheiten�,

Universität Hannover, Deutschland, Versuchsdurchführung am AIT, Thailand.

Stipendien und Auszeichungen

• Jahrgangsbester B. Sc.-Abschluß (1/80) • Stipendium der Keidanren Foundation Fellowship, Japan für das Master-Studium am

Asian Institute of Technology, Bangkok (Januar 1995 - August 1996). • MERIT-Stipendium für ausgezeichnete akademische Leistungen im B. Sc.�Studium. • Forschungsstipendium der DANIDA-Stiftung für die Durchführung der Masterarbeit

Arbeitserfahrung 1997 – 2001 IPM-Berater für Gemüsebau, Food & Agril. Organisation of the United

Nations (FAO), Bangladesh, Thailand, Laos, Kambodscha und Vietnam. 2001 – 2002 Landwirtschaftsberater, AME (bilaterales Projekt, Niederlande/Indien),

Bangalore, Indien. 2002 – 2005 Doktorand, �Protected Cultivation � an approach for sustainable vegetable

production in the humid tropics�, Thailand & PTD IPM-Berater des �Vegsys- Projektes (EU-China-Vietnam).

Mitgliedschaften Mitglied auf Lebenszeit der Indian Society of vegetable sciences Wissenschaftliche Veröffentlichungen

• Tinsely, R. L., P. Kumar, and D.T.T. Huyen. 1998. Chemical usages on Vegetables in Asia. Workshop on Sustainability of Horticulture Systems in Southeast Asia, AIT, Thailand, 1-3 April, 1998.

• Kumar, P., S. Johnsen and R. L. Tinsley. 2000. Life Cycle Studies on Fruit and Shoot borer (Leucinodes orbonalis; Pyralidae; Lepidopetra) and natural enemies of eggplant (Solanum melongena) insect-pests, Journal of Applied Biology, Vol. 10 (2), 2000.

• Kumar, P., S. Johnsen and R. L. Tinsley. 2000. Effect of Insecticide on population of fruit and shoot borer (Leucinodes orbonalis Gness; Pyralidae; Lepidopetra) secondary pests and natural enemies of eggplant (Solanum melongena), Journal of Applied Biology, Vol. 10 (1), 2000.

• Kumar, P., S. Johnsen and R. L. Tinsley. 2000. Insecticide use in eggplant (Solanum melongena) and related extension issues in Indo-Gangetic plains of North Bihar, Journal of Applied Biology, Vol. 10 (1), 2000.

• Ketalaar, J. W. K., and P. Kumar. 2002. Vegetable Integrated Production and Pest Management: the case for farmers as IPM Expert. International Conference on Vegetables held at the ITC Hotel Windsor Sheraton and Towers, Bangalore, India, 11-14 November 2002.

• Kumar, P., H.- M. Poehling, and C. Borgemeister. 2005. Effects of Different Application Methods of Neem against Sweetpotato Whitefly Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) on Tomato plants. Journal of Applied Entomology. 129:489�497.

Beiträge in Büchern • Tinsley, R. L. 2004. Developing Smallholder Agriculture: A Global Approach, AgBe

Publishing, Brussels, Belgium. Contributor: Chapter 6 Sustainability of Smallholder Agriculture.

138

Eidesstattliche Erklärung

Hiermit erkläre ich an Eides statt, dass die vorliegende Dissertationnicht schon

als MSc-Arbeit oder eine ähnliche Prüfungsarbeit verwendet worden ist.

.

.....................................

(Prabhat Kumar)

9 December 2005

Bangkok, Thailand

Documents

Final Thesis 140206